Time units are the intervals on which activities and other objects are based. The time unit may not differ from activity to activity—once set, it applies to all objects within the schedule. Durations, dates, and float values are all calculated according to the schedule’s time unit.
By default, the schedule time unit can only be set to days. For example, an activity’s duration may span one day or any whole unit increment thereof. If PolyTime is enabled, however, the schedule time unit may be set to a unit as small as minutes or as large as years.
Small time units—like minutes and hours—are useful for projects with short durations or for showing an extremely high level of detail. Large time units—like months and years—are useful for projects with long durations or for showing an extremely broad level of detail.
When NetPoint is installed, a default time unit must be selected. All new schedules will initially inherit this time unit, but a different time unit may be chosen at any time during planning.
To change the time unit, click the Schedule Properties icon , or select from the menu bar and choose the Dates tab.
If the schedule is blank (i.e. no activities or other objects have been drawn), the time unit can be changed to a higher or smaller unit. The Calendar Dates and Project Dates will automatically update to a reasonable range.
However, once an object has been placed on the canvas, the time unit may be changed only to a smaller unit. The Calendar Dates and Project Dates will remain fixed. This restriction is enforced because converting to a larger time unit would involve either rounding or truncation and would potentially result in changes to dates and durations (which would result in altered gaps, floats, drifts, etc.).
Pixel Resolution Requirements
Small time units can only be used if the duration of the project is reasonably short or if the size of the canvas is sufficiently large. Otherwise, the width of a time unit would be less than the width of a pixel on screen, and input from the mouse would no longer translate accurately on the canvas. Factors which affect the ratio of pixels to time units are:
- Schedule time unit
- Duration of the schedule (calendar start and end dates)
- Size of the canvas (page size chosen for print)
- Print Tiling
- Monitor resolution
If any of the above factors are changed which result in a schedule with less than one pixel per time unit, the Resolution Violation Alert window will open until the situation is corrected, which may take more than one adjustment. If it does, the dialogue box will prompt you as necessary.
If you choose to increase the page size you will be prompted to print. Clicking “Cancel” at that point will only cancel the printing; the adjustment will still happen.
When planning in days, weeks, half-months, months, quarters, or years, an activity’s finish date (and a finish milestone, finish benchmark, finish embed, and project completion) always points to the end of the prior unit. For example, a three-day activity that starts on May 1st will end on May 3rd at 11:59 pm. Similarly, a three-month activity that starts on January 1st will end on March 31st at 11:59 pm.
Any time units smaller than days, however, behave differently: the finish date always points to the start of the next unit. For example, a three-hour activity that starts at 1:00 pm will end at 4:00 pm, not 3:59:59. This is done to align with other applications as well as user expectations. However, there are a few consequences.
Take the previous example: a three-day activity that starts on May 1st will end on May 3rd at 11:59 pm. If the schedule is converted to hours, however, that same activity will now end on May 4th at 12:00 am. The same goes for finish milestones, benchmarks, embed, and the project completion. So while it may appear that the date is changing, it is only realigning depending on the time unit. All float calculations and values will remain constant.
When using PolyTime, resource assignments may be inaccurate under the following scenarios: 1) when converting plans from a higher time unit to a lower time unit, and 2) when exporting a plan that is in any time unit other than days. For example, if 48 widgets are assigned per day and the time unit is changed to hours, then 48 widgets would be assigned per hour instead of 2 widgets being assigned per hour. The following approaches may be taken to correct the outcome: 1) wait to resource load the schedule until the file is converted or exported; 2) reassign every resource to every activity after converting or exporting to correct the values; or 3) delete the resource assignments prior to converting or exporting and start with a clean resource-assignment slate, but with resources defined.
When working with time units of hours or smaller, NetPoint does not support “daily calendars” or “shifts”. For example, if a schedule in days is converted to hours, a working day is converted to 24 working hours. Similarly, a 1-day gap is converted to a 24 hour gap. As a result, hours, quarter-hours, and minutes are only recommended for schedules without non-work periods.