{"id":1227,"date":"2019-10-26T21:13:38","date_gmt":"2019-10-27T01:13:38","guid":{"rendered":"http:\/\/www.foxquestsystems.net\/foxblog\/?p=1227"},"modified":"2020-01-07T09:36:45","modified_gmt":"2020-01-07T14:36:45","slug":"the-partial-day-effect","status":"publish","type":"post","link":"https:\/\/www.foxquestsystems.net\/foxblog\/2019\/10\/26\/the-partial-day-effect\/","title":{"rendered":"The Partial Day Effect"},"content":{"rendered":"\n

Since most CPM scheduling performed in the construction industry measures time to the nearest day, calculating overall project durations by summing tasks containing units of measure less than a whole day should be strictly avoided. Keep in mind that schedulers are not timekeepers and they should resist the temptation to calculate the overall project time using durations more precise that a whole day. Furthermore, since schedulers typically record actual dates to the nearest day, it doesn\u2019t make sense to calculate future dates to anything more precise than whole days.<\/p>\n\n\n\n

The \u201cPartial Day\u201d (or Fractional Day) Effect is defined as:\n<\/p>\n\n\n\n

  1. Tasks\nthat do not start at the beginning of the day.<\/li>
  2. Tasks\nthat do not finish at the end of the day.<\/li>
  3. Tasks\nthat have non-integer day value for their Original or Remaining Duration.<\/li>
  4. Tasks\nthat have non-integer day value for their Total Float or Free Float.<\/li>
  5. Lags\nthat have non-integer day values.<\/li><\/ol>\n\n\n\n

    The Partial Day Effect manifests itself when upon browsing\nthe calculated dates in a CPM schedule; you or someone else notice activities\nare starting on the same day as its predecessor\u2019s finish date. This can cause\nconfusion especially with experienced CPM users who are accustomed to seeing\npredecessor finish dates completing on the day before (or just before) the\nsuccessor\u2019s start date. <\/p>\n\n\n\n

    In Figure 1 below, the User Preferences Time option is set to \u201cDo not show time\u201d. Note that the Early Finish date for Activity \u201cA1040 \u2013 Activity C1\u201d is 09-Jun-16 which is the same date for the Early Start of its successor, Activity \u201cA1050 \u2013 Activity F\u201d. In addition, Activity \u201cA1060 \u2013 Activity C2\u201d has the same Original and Remaining Duration as Activity C1 yet is not on the Critical Path. Furthermore, the layout is grouped by Total Float; however there are 2 separate groups for the same Total Float value of 0. How can this be?<\/p>\n\n\n\n

    \"\"
    Figure 1<\/figcaption><\/figure>\n\n\n\n

    In Figure 2 below, the User Preferences Time option is now set to \u201c24 hour (13:30)\u201d Under these settings, the Partial Day Effect is revealed by observing the Datetime format of Start and Finish dates.<\/p>\n\n\n\n

    \"\"
    Figure 2<\/figcaption><\/figure>\n\n\n\n

    The Partial Day Effect in this\nsituation was caused due to how each activity was statused. <\/p>\n\n\n\n

    1. A1020 was updated by assigning a Duration\nPercent Complete of 35%.<\/li>
    2. A1060 was updated by assigning a Remaining\nDuration (RD) of 16 days.<\/li><\/ol>\n\n\n\n

      P6 calculates the RD for A1020 as 25*(1-.35) or 16.25 Days.\nThe .25 remainder (or 2 hours) is reflected in the Finish date as 09-Jun-16\n10:00 (10AM). Meanwhile, A1060 displays the same RD as A1020; however, the Finish\ndate is reflected as 08-Jun-16 at 17:00 (5PM). Furthermore, A1060 is not on the\nCritical Path even though the Total Float (TF) value is displayed as 0 (the\nDuration Format Decimal value for the Day Unit of Time is set to 0). <\/p>\n\n\n\n

      The Partial Day Effect is also caused by how P6 stores dates and durations. In the typical P6 Duration fields such as Original Duration and Remaining Duration the default entry mode is to display durations in days. However, the actual duration value stored in the P6 database is in Hours. In the Figure 3 below, the activities in Figures 1 and 2 are shown with their native field names and values for their Original Duration (Target_drtn_hr_cnt); Remaining Duration (Remain_drtn_hr_cnt); Total Float (Total_float_hr_cnt);  and Free Float (Free_flt_drtn_hr_cnt).<\/p>\n\n\n\n

      \"\"
      Figure 3<\/figcaption><\/figure>\n\n\n\n

      The conversion occurs as a result of the Calendar setting value entered under the Hours\/Day textbox in the Hours per Time Period window as shown in Figure 4 below. <\/p>\n\n\n\n

      \"\"
      Figure 4<\/figcaption><\/figure>\n\n\n\n

      Since the Work-Hours per day entry is \u201c8\u201d in Hours\/Day, P6\nautomatically performs the \u201con-the-fly\u201d mathematical conversion as values are\nentered. Therefore, for Activity 1020, the Original Duration entry of 40 is\nnatively stored as 40*8 or 320 in the Task table\u2019s \u201cTarget_drtn_hr_cnt\u201d field.\nSimilarly, the Remaining Duration, calculated as 35% Complete, is stored as\n25*(1-.35)*8 or 130 in the Task table\u2019s \u201cRemain_drtn_hr_cnt\u201d field. <\/p>\n\n\n\n

      Storing data in hours, instead of days often causes the\nPartial Day Effect when \u201cmixed\u201d calendars are used.<\/p>\n\n\n\n

      Mixing Calendars\nin a CPM Network<\/strong><\/p>\n\n\n\n

      Typically, schedulers define their calendars to model whole days consistent with typical construction work environments in their area. For example, a typical calendar structure consists of a work-day that starts at 8:00AM, breaks for lunch from 12 Noon to 1:00PM and ends at 5:00PM for a total work-day of 8 Hours\/Day. Based on these parameters, a typical P6 5-Day Work-Week Global or Project Calendar would have the following configuration in Figure 5 below.<\/p>\n\n\n\n

      \"\"
      Figure 5<\/figcaption><\/figure>\n\n\n\n

      6-Day Work-Week and 7-Day Work-Week would follow the same configuration but with the added additional Nonwork days accordingly.<\/p>\n\n\n\n

      Often, this convention above is\nviolated when for example; a 24 Hour Calendar is used for concrete curing\nactivities or some other type of \u201cround-the-clock\u201d activity. For this reason, I\nstrongly discourage the use of 24-Hour calendar under any circumstance. For\nthese types of activities, a 7-Day Work Week Calendar based on an 8 Hour per\nday and no holidays is the best option and works just as well. Many articles \u201cfor\ninstructional purposes\u201d use a 24-Hour Calendar that is assigned to a concrete\ncuring activity or other \u201cround-the-clock\u201d activity. This option should be\navoided in real-time construction activities since it is problematic and is\noften the root cause of Partial Days.<\/p>\n\n\n\n

      In the Figure 6 below, two \u201c7-Day\nCure\u201d activities are used between a concrete pour activity and a concrete form\nactivity. Activity ST8420 is assigned to a 7-Day Calendar using an 8 Hour per\nday format. Activity ST78430 is assigned to a 7-Day Calendar using a 24 Hour per\nday format. Activity ST68920 and ST68180 are both assigned to a 5-Day \u201cField\u201d\nWork-Day Calendar using an 8 Hour per day format. The activities below are\ngrouped by Total Float value. Upon calculating the schedule, both Cure\nactivities finish on the same day, however, they both calculate a different\nTotal Float value.<\/p>\n\n\n\n

      The activity on the 7-Day\/8Hr calendar correctly calculates the starting and finish date while the activity on the 7-Day\/24Hr calendar starts on the same day as the Pour Footing activity (18-Oct-19). Also, the overall duration is shown as 7 Days but based on the displayed Start and Finish date equates to 8 Days.<\/p>\n\n\n\n

      In addition, there is an apparent discrepancy in the Free Float values. Since 25-Oct-19 falls on a Friday, the Cure activity on the 7-Day\/8Hr Calendar correctly calculates the Free Float as 2 Days since the successor, Activity ST6810 start on Monday, 28-Oct-19. The Free Float on the 7-Day\/24Hr Calendar incorrectly calculates the Free Float as 3 Days as shown below in Figure 6.<\/p>\n\n\n\n

      \"\"
      Figure 6<\/figcaption><\/figure>\n\n\n\n

      When the Time option is set to 24 Hours, the following values appear in Figure 7 below.<\/p>\n\n\n\n

      \"\"
      Figure 7<\/figcaption><\/figure>\n\n\n\n

      Note that the 24 Hour time\nsetting reveals additional information to clear up the confusion. Note that the\nstart time for Activity ST84730 is 17:00 (5:00PM). Since this activity is on a\n24 Hour calendar, it starts immediately after its predecessor\u2019s finish date.\nActivity ST78420 and ST87430 both correctly finish at the same time.<\/p>\n\n\n\n

      When the Duration value option is changed to 2 decimal places, the Original Duration, Remaining Duration, Total Float and Free Float reveal the actual calculated Duration values in Figure 8 below.<\/p>\n\n\n\n

      \"\"
      Figure 8<\/figcaption><\/figure>\n\n\n\n

      Note that the Total Float and\nFree Float values for Activity ST78430 are displayed as 2.63. This calculation\nis derived from the difference between the Late Finish and Early Finish.  Since the Late Finish is 28-Oct-19 at 08:00\nand the Early Finish is 25-Oct-19 at 17:00, the difference is 63 Hours\/24 Hours\nper Day or 2.63 Days (rounded to the nearest hundredth) as a direct result of\nusing a 7-Day\/24Hr Calendar. <\/p>\n\n\n\n

      Since calculating Project\ndurations to the nearest whole day is preferred, the use of a 7-Day\/24Hr\nCalendar is a root cause of the Partial Day Effect and therefore should be\navoided. The Duration values compound when successor activities are later in\nthe CPM network. This is because Total Float values are calculated based on the\nactivity\u2019s assigned Calendar.<\/p>\n\n\n\n

      Generating Partial Day Durations<\/strong><\/p>\n\n\n\n

      There are many ways to generate Partial Day durations. Of these include:<\/p>\n\n\n\n

      1. Entering a Percent Complete value for an activity assigned with \u201cDuration Percent Complete\u201d. For example, if an activity has an Original Duration of 3 days and a Duration Percent Complete is assigned 50%, then the activity will start at 8:00AM then having 1.5 Days remaining will complete at Noon on the second Day.
        <\/li>
      2. Not assigning a whole Day value to a Remaining Duration. For example, if 1.5 Days is assigned as the Remaining Duration, then the Finish Date will complete at Noon.
        <\/li>
      3. An activity has a Calendar assignment that is not consistent with a typical hour per day format.
        <\/li>
      4. Assigning non-standard Calendars then using lags between activities with mixed format calendars. <\/li><\/ol>\n\n\n\n

        However Partial Days are generated, they usually have a\ncascading effect through the CPM network that can make resolving this issue a\ndifficult and painful task. Suppose for example, the first activity of a long\nCPM network path completes at 2:00PM. Then its next driving successor activity\nwill start at 2:00PM on the same day and end at 2:00PM on its last day. This\nbehavior will continue to cascade throughout the CPM network until there are no\ndriving successors.<\/p>\n\n\n\n

        Determining if your CPM network contains\nPartial Days is easy! Simply;<\/p>\n\n\n\n

        1. Go to the User Settings and select the option to turn on time as shown in Figure 9 below.
          <\/li>
        2. Then, set Durations to display values to either 1 or 2 Decimal places shown in Figure 10 above. <\/li><\/ol>\n\n\n\n
          \"\"
          Figure 9
          <\/figcaption><\/figure>\n\n\n\n
          \"\"
          Figure 10<\/figcaption><\/figure>\n\n\n\n

          Once this is done, you can browse the activities Start and Finish Dates to detect activities not starting at 8:00AM or not ending at 17:00PM.<\/p>\n\n\n\n

          Z\u00fcmmer Analysis Reports <\/strong><\/p>\n\n\n\n

          Z\u00fcmmer contains the following reports to help resolve Partial Days (See also Figure 11 below):<\/p>\n\n\n\n

          1. Analysis Report #26 \u2013 \u201cActivities with Partial Day Durations\u201d<\/li>
          2. Analysis Report #27 \u2013 \u201cRelationships with Partial  Lag\u201d<\/li>
          3. Analysis Report \u2013 \u201cNot Completed Tasks with Partial Original or Remaining Durations\u201d<\/li>
          4. Analysis Report \u2013 \u201cIn-Progress Tasks with Partial Remaining Duration\u201d<\/li><\/ol>\n\n\n\n
            \"\"
            Figure 11<\/figcaption><\/figure>\n\n\n\n

            Z\u00fcmmer Analysis Report #26 \u2013 \u201cActivities with Partial Day Durations\u201d (Figure 12 below) is a comprehensive report listing any activity containing a Partial duration in the Original Duration, Remaining Duration, Free Float or Total Float values. The report sorts by Activity ID and lists the Activity Status, Activity ID, Activity Name, Partial Original Duration, Partial Remaining Duration, Partial Total Float and Partial Free Float values. <\/strong><\/p>\n\n\n\n

            \"\"
            Figure 12<\/figcaption><\/figure>\n\n\n\n

            Z\u00fcmmer Analysis Report #27 \u2013 \u201cRelationships with Partial\nLag\u201d (Figure 13 below) is a comprehensive report listing any Partial Lags. <\/p>\n\n\n\n

            Partial lags have a most insidious impact towards generating Partial Days. Changing the predecessor or successor activity to a standard Calendar does not necessarily guarantee that the lag will change in kind. Even in a moderately sized CPM network, finding these offending lags are very difficult using P6 alone.<\/p>\n\n\n\n

            \"\"
            Figure 13<\/figcaption><\/figure>\n\n\n\n

            Z\u00fcmmer Analysis Report \u2013 \u201cNot Completed Tasks with Partial Original or Remaining Durations\u201d (Figure 14 below) is a subset of Analysis Report #26 displayed above. <\/p>\n\n\n\n

            \"\"
            Figure 14<\/figcaption><\/figure>\n\n\n\n

            Not Completed Tasks with partial\nOriginal or Remaining durations have a higher priority with regards to\nresolving Partial Days because they tend to produce a cascading effect to\nsuccessor activities starting or ending in the middle of the day. Once these\nactivities are normalized, i.e. adjusted to containing whole day values,\nsuccessor activities in general will \u2018fall in line\u2019 starting at the beginning\nof the day and ending at the end of the day.<\/p>\n\n\n\n

            Z\u00fcmmer Analysis Report \u2013 \u201cIn\nProgress Activities with Partial Durations\u201d (Figure 15 below) is a subset of\nAnalysis Report #26 displayed above. <\/p>\n\n\n\n

            \"\"
            Figure 15<\/figcaption><\/figure>\n\n\n\n

            In-progress tasks with partial Remaining Durations also have a higher priority with regards to resolving because they tend to produce a cascading effect to successor activities starting or ending in the middle of the day. Once these activities are normalized, i.e. adjusted to containing whole day values, successor activities in general will \u2018fall in line\u2019 starting at the beginning of the day and ending at the end of the day.<\/p>\n\n\n\n

            Conclusion<\/strong><\/p>\n\n\n\n

            A few tips to avoid Partial Days in the first place:<\/p>\n\n\n\n

            1. When performing a schedule update, turn on time to ensure calculated results start at 8:00AM and end at 5:00PM (or at your typical Start and Finish times).<\/li>
            2. When performing a schedule update, set the Duration decimal to 1 (or 2) to view duration values in tenths.<\/li>
            3. When declaring the Data Date, always set time on and set the Data Date time to include your typical Start time.<\/li>
            4. When assigning start constraints, turn on time and set the constraint to include your typical Start time.<\/li>
            5. When assigning finish constraints, turn on time and set the constraint to include your typical Finish time.<\/li>
            6. When setting \u201cMust Finish By\u201d constraints for the Project, turn on time and set the date to include your typical Finish time.<\/li>
            7. Use consistent \u201cHours per Day\u201d configured Calendars especially when a lag value is assigned.<\/li>
            8. Update in-progress activities based on Remaining Duration in whole days or;<\/li>
            9. Update in-progress activities based on a completion date to include your typical Finish time.<\/li>
            10. For consistency, when actualizing start dates, save Actual Start dates to include your typical Start time.<\/li>
            11. For consistency, when actualizing finish dates, save Actual Finish dates to include your typical Finish time.<\/li>
            12. If someone asks you to do an analysis or \u2018What-if\u2019 the work is accelerated from an 8 Hour day to a 10 Hour day, suggest doing the analysis on a 6 Day Work-Week instead of a 5 Day Work-Week. The difference in calculations is between a 50 Hour week and a 48 Hour week which for scheduling purposed should be acceptable.<\/li><\/ol>\n\n\n\n

              Keeping a neat, tidy and \u201cwholesome\u201d CPM network with no Partial Days is an important part of a Scheduler\u2019s QA\/QC routine. <\/p>\n\n\n\n

              Copyright \u00a92019 FoxQuest Systems, Inc. – All Rights Reserved<\/p>\n\n\n\n


              <\/strong><\/p>\n","protected":false},"excerpt":{"rendered":"

              Finding and eliminating “Partial Days” is an important part of a Scheduler’s QA\/QC routine.<\/p>\n

              A deeper look into the Partial Day Effect<\/p>\n","protected":false},"author":2,"featured_media":1228,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"nf_dc_page":"","om_disable_all_campaigns":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_post_was_ever_published":false},"categories":[2,12],"tags":[],"class_list":["post-1227","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-analysis","category-tips"],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"https:\/\/i0.wp.com\/www.foxquestsystems.net\/foxblog\/wp-content\/uploads\/2019\/10\/Screen-Shot-Partial-Days-4-Available-Reports.jpg?fit=833%2C466&ssl=1","_links":{"self":[{"href":"https:\/\/www.foxquestsystems.net\/foxblog\/wp-json\/wp\/v2\/posts\/1227","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.foxquestsystems.net\/foxblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.foxquestsystems.net\/foxblog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.foxquestsystems.net\/foxblog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.foxquestsystems.net\/foxblog\/wp-json\/wp\/v2\/comments?post=1227"}],"version-history":[{"count":13,"href":"https:\/\/www.foxquestsystems.net\/foxblog\/wp-json\/wp\/v2\/posts\/1227\/revisions"}],"predecessor-version":[{"id":1450,"href":"https:\/\/www.foxquestsystems.net\/foxblog\/wp-json\/wp\/v2\/posts\/1227\/revisions\/1450"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.foxquestsystems.net\/foxblog\/wp-json\/wp\/v2\/media\/1228"}],"wp:attachment":[{"href":"https:\/\/www.foxquestsystems.net\/foxblog\/wp-json\/wp\/v2\/media?parent=1227"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.foxquestsystems.net\/foxblog\/wp-json\/wp\/v2\/categories?post=1227"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.foxquestsystems.net\/foxblog\/wp-json\/wp\/v2\/tags?post=1227"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}