# Compute difference between dates¶

Compute the difference between an ISO-8601 formatted date column (yyyy-MM-ddTHH:mm:ss.SSSZ) and another time reference: the current time, a fixed date, or another column.

## Options¶

Time since column

Column containing data in ISO-8601 format. Use a Prepare step to parse your data into this format if it isn’t already.

Until

Choose the second time reference to compute the difference — now, another date column, or a fixed date.

Output time unit

Determine the unit of time in which to express the datetime difference — year, month, week, day, hour, minute or second.

Output column

Column into which the datetime difference will be written.

Reverse output

Multiply the computed difference by -1, reversing it: 3 days-3 days.