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# Date Difference
## Description
When using this part, the system returns the difference between two date-time variables, in a group (user-defined) that holds the difference in terms of seconds, minutes, hours, days, months and years.
## Use
This part allows users to assess how much time has passed between two events, or between a previous/future date and today (using now() as one of the date inputs). The output collection contains the difference in values in various time units of measure, as well as a flag to show whether the difference is positive or negative (whether the second input date is after or before the first).
## Editor Fields
| Field Name | Description/Use | Type/Options | Optional/Mandatory |
| ---------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ----------------- | ------------------ |
| Group | This field contains the group name within which the system stores the results. | Container Name | Mandatory |
| Input type | This field allows the user to specify whether the date inputs are standard (YYMMDD.HHMMSS) or Epoch dates. | Standard \| Epoch | Mandatory |
| Date 1 | This is the data object used as the start date in the calculation of difference.
If left blank this date will default to the exact date/time assessed during runtime.
| Data Object\* | Optional\*\* |
| Date 2 | This is the data object used as the end date in the calculation of difference.
If left blank this date will default to the exact date/time assessed during runtime.
| Data Object\* | Optional\*\* |
| Mode | This is the "resolution" of the calculation and can be set to date or date and time. | date \| datetime | Mandatory |
**Part Editor Notes:**
\* Date inputs require the user to enter the $() data object construction.
\*\* If left blank the input is assumed to be now (current date and time), assessed at runtime (ie not the date the logic was modelled)
## Mode
Choosing the mode **calculate date difference** will ignore any timestamps included in the dates, and the output will not include hours or minutes except totals.
## Output
The date difference is output as objects in a group using the following naming conventions
* years, months, days, hours, minutes, seconds all calculate the **time-unit-specific** **whole number** **difference** of between that time unit in each date e.g.
the **hours** difference of January 1st 9pm and January 3rd 9am is 12; the **days** difference is 1 (1 day to Jan 2nd pm, then a partial day to Jan 3rd am)
* total\_years, total\_months, total\_days, and total\_hours all calculate the **total number** of time units between the dates.
The **total\_hours** difference of January 1st 9pm and January 3rd 9am is 36 (24 + 12). The total\_days difference is 1 (only 1 whole day between the dates).
* counted\_years, counted\_months, and counted\_days all calculate the total number of time units between the dates, but the system rounds them up in cases of fractional periods.
The counted hours difference is 36 (no rounding required). The counted\_days difference is 2 (the 1st to the 3rd is 2 days, rounding up for the partial day).
* negative is set to 0 when the second input date is LATER than the first. In the event Date2 is EARLIER than Date1, negative is set to 1.
## Example
Using input dates of July 1st 2016 and April 28 2017 and defining the group as "diff" gives the following results in the context. Calculations are done for total difference and unit difference for seconds, minutes, hours, days, months and years.
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