BUG: DatetimeIndex.is_year_start breaks on double-digit frequencies

[MarcoGorelli]

BUG: DatetimeIndex.is_year_start breaks on double-digit frequencies

[VISWESWARAN1998]

take

[VISWESWARAN1998]

Replaced absolute string slicing into split to resolve this issue

# YearBegin(), BYearBegin() use month = starting month of year.
# QuarterBegin(), BQuarterBegin() use startingMonth = starting
# month of year. Other offsets use month, startingMonth as ending
# month of year.
period_str = "".join([dt_char for dt_char in list(freqstr.split("-")[0]) if not dt_char.isdigit()])
if (period_str in ["MS", "QS", "YS"]):
    end_month = 12 if month_kw == 1 else month_kw - 1
    start_month = month_kw

Gives me

[4/4] Linking target pandas/_libs/tslibs/fields.cpython-310-x86_64-linux-gnu.so
[ True  True]

[MarcoGorelli]

I don't think this is the solution, we need to go up some levels and look for something like freq.n

@natmokval you'd done a bunch of work in this area, so this might be interesting to you to try fixing?

[VISWESWARAN1998]

I don't think this is the solution, we need to go up some levels and look for something like freq.n

@natmokval you'd done a bunch of work in this area, so this might be interesting to you to try fixing?

Can you elaborate more on this one?

[natmokval]

@natmokval you'd done a bunch of work in this area, so this might be interesting to you to try fixing?

Yeah, sure, I would like to work on this.

[VISWESWARAN1998]

period_str = "".join([
    dt_char for dt_char in list(freqstr.split("-")[0]) if not dt_char.isdigit()
])

Splits the freqstr and removes the digits. So it can properly parse 10MS, 10YS-JAN, 2B etc., I believe it is more viable option to absolute slicing