This feature allows you to create a variable, based on an existing date variable, or from questionnaire data like interview start time, into a new variable with intervals.
To access this feature, in the edit menu select create a variable..., then select sliding dates.
The following options are available:
Date used: Select the date on which you want to base the new variable (the start or end time of the interview, the start, midpoint or end of an askiasurf wave, or an existing date question in the project).
Question: If you are basing the new variable on an existing date question, click ... to select the question.
Scale: Select the granularity of the new question. For example, if you want a category in the question for every day, select day.
Size: Specify the time interval to be used. For example, if in scale you selected day, then entering 1 here will create a category for each day, while entering 2 would create a category for every other day.
Shift: This is an optional offset for the threshold for each time segment (i.e. the point in time at which one time segment ends and another begins). For example, if in scale you selected day, then entering 1 will create categories beginning one hour before the end of each day (i.e. at 23:00 hours).
Format: Select the format in which you want the category descriptions to appear. For example, you can select dd/MM/yyyy (i.e. dates only in day/month/year format) or dd/MM/yyyy hh:mm (i.e. dates and times in day/month/year hour/minute format).
Display as interval: If this option is selected, the start and end dates/times are displayed, in the new question's category descriptions, for each time interval. If the option is not selected, then only the start times are given for each time interval.
All values: If selected, a category is created for every time interval.
Remove blanks: If this option is selected, categories with counts of zero will not be created. Note: This option is available only if all values is selected.
Last...: If selected, a category is created for the last N time intervals, where N is the number you specify. For example, if the scale is set to day, and you enter 10 here, then categories are created for the last 10 days only.
From determines the point from which the last N time intervals are counted:
Last observed: the last N intervals from the last observed interval are included (e.g. if date used is set to interview start, then the last N intervals before the last recorded interview start date are included).
Now: the last N intervals as of now.
Specified date: the last N intervals as of the specified date (select a date in the adjacent box).