Description

The Ireland calendar (holidays.IE / holidays.Ireland) does not include substitute bank holidays when fixed-date public holidays fall on weekends. Irish banks observe the following Monday as a substitute holiday in these cases.

Current Behavior

import holidays
from datetime import date

cal = holidays.IE(years=2020)

# St. Stephen's Day 2020 falls on Saturday (Dec 26)
print(date(2020, 12, 26) in cal)  # True
print(date(2020, 12, 28) in cal)  # False - but should be True (substitute Monday)

Expected Behavior

When fixed-date Irish public holidays fall on weekends, the following Monday should be included as an observed/substitute holiday:

• New Year's Day (Jan 1)
• St. Patrick's Day (Mar 17)
• Christmas Day (Dec 25)
• St. Stephen's Day (Dec 26)

This is consistent with how holidays.UK handles substitute bank holidays.

Real-World Examples

Edge Case: Both Christmas and St. Stephen's on Weekend (2021)

When both holidays fall on a weekend (Dec 25 = Saturday, Dec 26 = Sunday), two substitute days are needed:

• Dec 27 (Monday) = Christmas Observed
• Dec 28 (Tuesday) = St. Stephen's Observed

Reference

Irish bank holiday rules are governed by the Organisation of Working Time Act 1997. When a public holiday falls on a weekend, the substitute day is typically the next working day (Monday).

• Citizens Information - Public Holidays

Use Case

This is important for financial calculations (loan interest, lease payments, derivatives) where business day adjustments are required.

Workaround

from datetime import date, timedelta
from holidays.countries import Ireland

class FinancialIreland(Ireland):
    def _populate(self, year):
        super()._populate(year)
        self._add_observed(date(year, 1, 1))
        self._add_observed(date(year, 3, 17))
        self._add_observed(date(year, 12, 25))
        self._add_observed(date(year, 12, 26))

    def _add_observed(self, dt: date) -> None:
        if dt not in self:
            return
        holiday_name = self[dt]
        if dt.weekday() == 5:  # Saturday -> Monday
            target = dt + timedelta(days=2)
        elif dt.weekday() == 6:  # Sunday -> Monday
            target = dt + timedelta(days=1)
        else:
            return
        # Handle collision when both Christmas and St. Stephen's on weekend
        if target in self and "(Observed)" in self.get(target, ""):
            target = target + timedelta(days=1)
        self[target] = f"{holiday_name} (Observed)"

Environment

• holidays version: 0.90
• Python version: 3.10+