How to convert a column date into another column with ordinal number of days

Dear Knimers,
I have grouped a dataset (grouped by date, one date by row) along a series of a few years. Now I need to convert each row into a new column with their ordinal number of days. For instance:
Date column → Day#
2021-10-12 → 1
2021-10-13 → 2
2021-10-14 → 3
2021-10-15 → 4
and so on.
Could someone give any suggestion?
Thanks for any help.

The logic in this table isn’t clear to me. How did you come up with the values in the Day# column?

Assuming you have a properly formatted date column, the Extrace Date&Time Fields nodes would give you an ordinal day number, but it won’t be what you showed here.


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I would use this node and set the granularity to days.

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