[Python] Grouping Time-series Data Interannual

I've been using groupby() for a bit but am running into a problem with grouping inter-annual (i.e., spanning two or more years).

I've got a simple dataframe that I want to group by 365D intervals beginning from a specific start date.

date data
2018-03-14 0.000000
2018-03-15 0.000000
2018-03-16 0.000006
2018-03-19 -0.000469
2018-03-20 -0.001312
... ...
2025-04-10 0.082415
2025-04-11 0.002901
2025-04-14 0.005738
2025-04-15 0.007664
2025-04-16 0.012883
1848 rows × 1 columns


I'm assuming it can be solved with pd.Grouper or pd.TimeGrouper but am having trouble sorting it out.

I'm familiar using pd.date_range(start, end, freq=DateOffset(days=365)), but I can't make my way back using pd.Grouper.

Python 3.11.12

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