| Unit | Returns |
|---|---|
| "Y" | The number of complete years in the period |
| "M" | The number of complete months in the period |
| "D" | The number of days in the period |
| "MD" | The difference between the days in start_date and end_date. The months and years of the dates are ignored |
| "YM" | The difference between the months in start_date and end_date. The days and years of the dates are ignored |
| "YD" | The difference between the days of start_date and end_date. The years of the dates are ignored |
Be careful of Leap Year calculations when the units ignore years. For example:
=datedif("2010-01-01","2010-07-21","YD")
returns 201 days
=datedif("2016-01-01","2016-07-21","YD")
returns 202 days