Standard Weeks

Standard Weeks are widely used in biological recording and these differ slightly from conventional or fiscal weeks.

The idea is that each calendar day is always in the same week whatever the year.

Standard weeks are defined as follows:

  • Jan 1st always starts week 1
  • If the year is a leap year then leap day (29th Feb) is included in week 9 and all subsequent days stay in the same week they would have been in if it were a non-leap year
  • The last day of December, that would form a 'week 53', is included in week 52

For example, today (Mon 25th October 2021) is in Week 43.

A perpetual week calendar is given below (valid for any year):

WeekDates (inclusive)
11st January to 7th January
28th January to 14th January
315th January to 21st January
422nd January to 28th January
529th January to 4th February
65th February to 11th February
712th February to 18th February
819th February to 25th February
926th February to 4th March (including 29 February in a Leap Year)
105th March to 11th March
1112th March to 18th March
1219th March to 25th March
1326th March to 1st April
142nd April to 8th April
159th April to 15th April
1616th April to 22nd April
1723th April to 29th April
1830th April to 6th May
197th May to 13th May
2014th May to 20th May
2121st May to 27th May
2228th May to 3rd June
234th June to 10th June
2411th June to 17th June
2518th June to 24th June
2625th June to 1st July
272nd July to 8th July
289th July to 15th July
2916th July to 22nd July
3023rd July to 29th July
3130th July to 5th August
326th August to 12th August
3313th August to 19th August
3420th August to 26th August
3527th August to 2nd September
363rd September to 9th September
3710th September to 16th September
3817th September to 23rd September
3924th September to 30th September
401st October to 7th October
418th October to 14th October
4215th October to 21st October
4322nd October to 28th October
4429th October to 4th November
455th November to 11th November
4612th November to 18th November
4719th November to 25th November
4826th November to 2nd December
493rd December to 9th December
5010th December to 16th December
5117th December to 23rd December
5224th December to 31st December (note this is an 8 day week)

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