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Week Numbers 1981
| Week # | Start date (Mon) | End date (Sun) |
|---|---|---|
| ▸ 1 | Mon, 29 Dec 1980 | Sun, 4 Jan 1981 |
| ▸ 2 | Mon, 5 Jan 1981 | Sun, 11 Jan 1981 |
| ▸ 3 | Mon, 12 Jan 1981 | Sun, 18 Jan 1981 |
| ▸ 4 | Mon, 19 Jan 1981 | Sun, 25 Jan 1981 |
| ▸ 5 | Mon, 26 Jan 1981 | Sun, 1 Feb 1981 |
| ▸ 6 | Mon, 2 Feb 1981 | Sun, 8 Feb 1981 |
| ▸ 7 | Mon, 9 Feb 1981 | Sun, 15 Feb 1981 |
| ▸ 8 | Mon, 16 Feb 1981 | Sun, 22 Feb 1981 |
| ▸ 9 | Mon, 23 Feb 1981 | Sun, 1 Mar 1981 |
| ▸ 10 | Mon, 2 Mar 1981 | Sun, 8 Mar 1981 |
| ▸ 11 | Mon, 9 Mar 1981 | Sun, 15 Mar 1981 |
| ▸ 12 | Mon, 16 Mar 1981 | Sun, 22 Mar 1981 |
| ▸ 13 | Mon, 23 Mar 1981 | Sun, 29 Mar 1981 |
| ▸ 14 | Mon, 30 Mar 1981 | Sun, 5 Apr 1981 |
| ▸ 15 | Mon, 6 Apr 1981 | Sun, 12 Apr 1981 |
| ▸ 16 | Mon, 13 Apr 1981 | Sun, 19 Apr 1981 |
| ▸ 17 | Mon, 20 Apr 1981 | Sun, 26 Apr 1981 |
| ▸ 18 | Mon, 27 Apr 1981 | Sun, 3 May 1981 |
| ▸ 19 | Mon, 4 May 1981 | Sun, 10 May 1981 |
| ▸ 20 | Mon, 11 May 1981 | Sun, 17 May 1981 |
| ▸ 21 | Mon, 18 May 1981 | Sun, 24 May 1981 |
| ▸ 22 | Mon, 25 May 1981 | Sun, 31 May 1981 |
| ▸ 23 | Mon, 1 Jun 1981 | Sun, 7 Jun 1981 |
| ▸ 24 | Mon, 8 Jun 1981 | Sun, 14 Jun 1981 |
| ▸ 25 | Mon, 15 Jun 1981 | Sun, 21 Jun 1981 |
| ▸ 26 | Mon, 22 Jun 1981 | Sun, 28 Jun 1981 |
| ▸ 27 | Mon, 29 Jun 1981 | Sun, 5 Jul 1981 |
| ▸ 28 | Mon, 6 Jul 1981 | Sun, 12 Jul 1981 |
| ▸ 29 | Mon, 13 Jul 1981 | Sun, 19 Jul 1981 |
| ▸ 30 | Mon, 20 Jul 1981 | Sun, 26 Jul 1981 |
| ▸ 31 | Mon, 27 Jul 1981 | Sun, 2 Aug 1981 |
| ▸ 32 | Mon, 3 Aug 1981 | Sun, 9 Aug 1981 |
| ▸ 33 | Mon, 10 Aug 1981 | Sun, 16 Aug 1981 |
| ▸ 34 | Mon, 17 Aug 1981 | Sun, 23 Aug 1981 |
| ▸ 35 | Mon, 24 Aug 1981 | Sun, 30 Aug 1981 |
| ▸ 36 | Mon, 31 Aug 1981 | Sun, 6 Sep 1981 |
| ▸ 37 | Mon, 7 Sep 1981 | Sun, 13 Sep 1981 |
| ▸ 38 | Mon, 14 Sep 1981 | Sun, 20 Sep 1981 |
| ▸ 39 | Mon, 21 Sep 1981 | Sun, 27 Sep 1981 |
| ▸ 40 | Mon, 28 Sep 1981 | Sun, 4 Oct 1981 |
| ▸ 41 | Mon, 5 Oct 1981 | Sun, 11 Oct 1981 |
| ▸ 42 | Mon, 12 Oct 1981 | Sun, 18 Oct 1981 |
| ▸ 43 | Mon, 19 Oct 1981 | Sun, 25 Oct 1981 |
| ▸ 44 | Mon, 26 Oct 1981 | Sun, 1 Nov 1981 |
| ▸ 45 | Mon, 2 Nov 1981 | Sun, 8 Nov 1981 |
| ▸ 46 | Mon, 9 Nov 1981 | Sun, 15 Nov 1981 |
| ▸ 47 | Mon, 16 Nov 1981 | Sun, 22 Nov 1981 |
| ▸ 48 | Mon, 23 Nov 1981 | Sun, 29 Nov 1981 |
| ▸ 49 | Mon, 30 Nov 1981 | Sun, 6 Dec 1981 |
| ▸ 50 | Mon, 7 Dec 1981 | Sun, 13 Dec 1981 |
| ▸ 51 | Mon, 14 Dec 1981 | Sun, 20 Dec 1981 |
| ▸ 52 | Mon, 21 Dec 1981 | Sun, 27 Dec 1981 |
| ▸ 53 | Mon, 28 Dec 1981 | Sun, 3 Jan 1982 |
About ISO 8601 Week Numbers
Under the ISO 8601 standard, weeks start on Monday and are numbered from 1 to 52 or 53. Week 1 is the week that contains the first Thursday of the year — equivalently, the week containing January 4th. As a result, the first few days of January can fall in the last week of the previous year, and the last days of December can fall in week 1 of the next year.
A year has 53 ISO weeks when it starts on a Thursday, or on a Wednesday in a leap year; otherwise it has 52. 1981 has 53 ISO weeks.