Week numbers 661

661 has 52 ISO weeks. Week 1: Dec 31, 660 – Jan 6, 661 · Week 52: Dec 23 – 29

661 at a glance

Weeks in 66152
Week 1December 31, 660 – January 6, 661
Week 52December 23, 661 – December 29, 661
Days in 661365
Leap yearNo

All Weeks in 661

Week From To Month
Week 1 in 661 December 31, 660 January 6, 661 December / January
Week 2 in 661 January 7, 661 January 13, 661 January
Week 3 in 661 January 14, 661 January 20, 661 January
Week 4 in 661 January 21, 661 January 27, 661 January
Week 5 in 661 January 28, 661 February 3, 661 January / February
Week 6 in 661 February 4, 661 February 10, 661 February
Week 7 in 661 February 11, 661 February 17, 661 February
Week 8 in 661 February 18, 661 February 24, 661 February
Week 9 in 661 February 25, 661 March 3, 661 February / March
Week 10 in 661 March 4, 661 March 10, 661 March
Week 11 in 661 March 11, 661 March 17, 661 March
Week 12 in 661 March 18, 661 March 24, 661 March
Week 13 in 661 March 25, 661 March 31, 661 March
Week 14 in 661 April 1, 661 April 7, 661 April
Week 15 in 661 April 8, 661 April 14, 661 April
Week 16 in 661 April 15, 661 April 21, 661 April
Week 17 in 661 April 22, 661 April 28, 661 April
Week 18 in 661 April 29, 661 May 5, 661 April / May
Week 19 in 661 May 6, 661 May 12, 661 May
Week 20 in 661 May 13, 661 May 19, 661 May
Week 21 in 661 May 20, 661 May 26, 661 May
Week 22 in 661 May 27, 661 June 2, 661 May / June
Week 23 in 661 June 3, 661 June 9, 661 June
Week 24 in 661 June 10, 661 June 16, 661 June
Week 25 in 661 June 17, 661 June 23, 661 June
Week 26 in 661 June 24, 661 June 30, 661 June
Week 27 in 661 July 1, 661 July 7, 661 July
Week 28 in 661 July 8, 661 July 14, 661 July
Week 29 in 661 July 15, 661 July 21, 661 July
Week 30 in 661 July 22, 661 July 28, 661 July
Week 31 in 661 July 29, 661 August 4, 661 July / August
Week 32 in 661 August 5, 661 August 11, 661 August
Week 33 in 661 August 12, 661 August 18, 661 August
Week 34 in 661 August 19, 661 August 25, 661 August
Week 35 in 661 August 26, 661 September 1, 661 August / September
Week 36 in 661 September 2, 661 September 8, 661 September
Week 37 in 661 September 9, 661 September 15, 661 September
Week 38 in 661 September 16, 661 September 22, 661 September
Week 39 in 661 September 23, 661 September 29, 661 September
Week 40 in 661 September 30, 661 October 6, 661 September / October
Week 41 in 661 October 7, 661 October 13, 661 October
Week 42 in 661 October 14, 661 October 20, 661 October
Week 43 in 661 October 21, 661 October 27, 661 October
Week 44 in 661 October 28, 661 November 3, 661 October / November
Week 45 in 661 November 4, 661 November 10, 661 November
Week 46 in 661 November 11, 661 November 17, 661 November
Week 47 in 661 November 18, 661 November 24, 661 November
Week 48 in 661 November 25, 661 December 1, 661 November / December
Week 49 in 661 December 2, 661 December 8, 661 December
Week 50 in 661 December 9, 661 December 15, 661 December
Week 51 in 661 December 16, 661 December 22, 661 December
Week 52 in 661 December 23, 661 December 29, 661 December

Calendars 661

January 661
MoTuWeThFrSaSu
Week 1123456
Week 278910111213
Week 314151617181920
Week 421222324252627
Week 528293031
February 661
MoTuWeThFrSaSu
Week 5123
Week 645678910
Week 711121314151617
Week 818192021222324
Week 925262728
March 661
MoTuWeThFrSaSu
Week 9123
Week 1045678910
Week 1111121314151617
Week 1218192021222324
Week 1325262728293031
April 661
MoTuWeThFrSaSu
Week 141234567
Week 15891011121314
Week 1615161718192021
Week 1722232425262728
Week 182930
May 661
MoTuWeThFrSaSu
Week 1812345
Week 196789101112
Week 2013141516171819
Week 2120212223242526
Week 222728293031
June 661
MoTuWeThFrSaSu
Week 2212
Week 233456789
Week 2410111213141516
Week 2517181920212223
Week 2624252627282930
July 661
MoTuWeThFrSaSu
Week 271234567
Week 28891011121314
Week 2915161718192021
Week 3022232425262728
Week 31293031
August 661
MoTuWeThFrSaSu
Week 311234
Week 32567891011
Week 3312131415161718
Week 3419202122232425
Week 35262728293031
September 661
MoTuWeThFrSaSu
Week 351
Week 362345678
Week 379101112131415
Week 3816171819202122
Week 3923242526272829
Week 4030
October 661
MoTuWeThFrSaSu
Week 40123456
Week 4178910111213
Week 4214151617181920
Week 4321222324252627
Week 4428293031
November 661
MoTuWeThFrSaSu
Week 44123
Week 4545678910
Week 4611121314151617
Week 4718192021222324
Week 48252627282930
December 661
MoTuWeThFrSaSu
Week 21
Week 492345678
Week 509101112131415
Week 5116171819202122
Week 5223242526272829
Week 13031

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Find the week number of a date

How week numbers are counted

Most of the world numbers weeks according to the ISO 8601 standard. A week starts on Monday, and week 1 is the week that contains the first Thursday of the year, which is always the week that contains 4 January.

Week 1 of 661 starts on December 31, 660 and ends on January 6, 661 (ISO 8601, Monday to Sunday). 661 has 52 ISO weeks.

Because of this rule, the first days of January can belong to the last week of the previous year, and the last days of December can belong to week 1 of the next year.

In the United States, weeks usually start on Sunday and week 1 is the week that contains 1 January, so the US week number can differ from the ISO week number.

Frequently Asked Questions (FAQ)

How many weeks does 661 have?

661 has 52 ISO weeks.

When does week 1 of 661 start?

Week 1 of 661 starts on December 31, 660 and ends on January 6, 661 (ISO 8601, Monday to Sunday).

When does the last week of 661 end?

Week 52 of 661 starts on December 23, 661 and ends on December 29, 661 (ISO 8601, Monday to Sunday).

Which years have 53 weeks?

The next years with 53 ISO weeks are 663, 668, 674, 680, 685.

Why do the US and Europe show different week numbers?

Europe follows ISO 8601: weeks start on Monday and week 1 is the week with the first Thursday of the year. In the US, weeks usually start on Sunday and week 1 is the week that contains 1 January, so the two numbers can differ by one.