Jinja template malfunctions once per year!

 - alias: Reminder_if_tomorrow_is_black_bins
    trigger:
      platform: template
      value_template: >
        {% set d = (strptime(states('sensor.binsdate'), '%d/%m/%y').timestamp() - 24*60*60)|timestamp_custom('%Y-%m-%d') %}{{ states('sensor.date_time') == d ~ ', 21:00' }}

sensor.binsdate = 29/03/2021
sensor.date_time = 2021-03-27, 21:00

This normally fires on Sunday evening, but has just fired now! I seem to recall it did this last year? Is it due to the clocks going forward or similar?! Anyone know?!