# Compute difference between dates[¶](https://doc.dataiku.com/dss/latest/preparation/processors/date-difference.html#compute-difference-between-dates "Permalink to this headline")

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[¶](https://doc.dataiku.com/dss/latest/preparation/processors/date-difference.html#options "Permalink to this headline")

**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`.
