1666/1667
For 1666/1667, the key weeks and dates were:
Week 1: 18 December to 25 December 1666
New Year 1667, Week 2: 25 December to 1 January 1667
Legal New Year, Week 14: 19 March to 26 March 1667
Week 52: 10 December to 17 December 1667
| Item Number -Wellcome | Week | Start Day | Start Month | End Day | End Month | Year | Item Number -Wellcome | Week | Start Day | Start Month | End Day | End Month | Year | |
| 1666-01 | 1 | 18 | December | 25 | December | 1666 | 1667-27 | 27 | 18 | June | 25 | June | 1667 | |
| 1666-02 | 2 | 25 | December | 1 | January | 1666 | 1667-28 | 28 | 25 | June | 2 | July | 1667 | |
| 1666-03 | 3 | 1 | January | 8 | January | 1666 | 1667-29 | 29 | 2 | July | 9 | July | 1667 | |
| 1666-04 | 4 | 8 | January | 15 | January | 1666 | 1667-30 | 30 | 9 | July | 16 | July | 1667 | |
| 1666-05 | 5 | 15 | January | 22 | January | 1666 | 1667-31 | 31 | 16 | July | 23 | July | 1667 | |
| 1666-06 | 6 | 22 | January | 29 | January | 1666 | 1667-32 | 32 | 23 | July | 30 | July | 1667 | |
| 1666-07 | 7 | 29 | January | 5 | February | 1666 | 1667-33 | 33 | 30 | July | 6 | August | 1667 | |
| 1666-08 | 8 | 5 | February | 12 | February | 1666 | 1667-34 | 34 | 6 | August | 13 | August | 1667 | |
| 1666-09 | 9 | 12 | February | 19 | February | 1666 | 1667-35 | 35 | 13 | August | 20 | August | 1667 | |
| 1666-10 | 10 | 19 | February | 26 | February | 1666 | 1667-36 | 36 | 20 | August | 27 | August | 1667 | |
| 1666-11 | 11 | 26 | February | 5 | March | 1666 | 1667-37 | 37 | 27 | August | 3 | September | 1667 | |
| 1666-12 | 12 | 5 | March | 12 | March | 1666 | 1667-38 | 38 | 3 | September | 10 | September | 1667 | |
| 1666-13 | 13 | 12 | March | 19 | March | 1666 | 1667-39 | 39 | 10 | September | 17 | September | 1667 | |
| 1667-14 | 14 | 19 | March | 26 | March | 1667 | 1667-40 | 40 | 17 | September | 24 | September | 1667 | |
| 1667-15 | 15 | 26 | March | 2 | April | 1667 | 1667-41 | 41 | 24 | September | 1 | October | 1667 | |
| 1667-16 | 16 | 2 | April | 9 | April | 1667 | 1667-42 | 42 | 1 | October | 8 | October | 1667 | |
| 1667-17 | 17 | 9 | April | 16 | April | 1667 | 1667-43 | 43 | 8 | October | 15 | October | 1667 | |
| 1667-18 | 18 | 16 | April | 23 | April | 1667 | 1667-44 | 44 | 15 | October | 22 | October | 1667 | |
| 1667-19 | 19 | 23 | April | 30 | April | 1667 | 1667-45 | 45 | 22 | October | 29 | October | 1667 | |
| 1667-20 | 20 | 30 | April | 7 | May | 1667 | 1667-46 | 46 | 29 | October | 5 | November | 1667 | |
| 1667-21 | 21 | 7 | May | 14 | May | 1667 | 1667-47 | 47 | 5 | November | 12 | November | 1667 | |
| 1667-22 | 22 | 14 | May | 21 | May | 1667 | 1667-48 | 48 | 12 | November | 19 | November | 1667 | |
| 1667-23 | 23 | 21 | May | 28 | May | 1667 | 1667-49 | 49 | 19 | November | 26 | November | 1667 | |
| 1667-24 | 24 | 28 | May | 4 | June | 1667 | 1667-50 | 50 | 26 | November | 3 | December | 1667 | |
| 1667-25 | 25 | 4 | June | 11 | June | 1667 | 1667-51 | 51 | 3 | December | 10 | December | 1667 | |
| 1667-26 | 26 | 11 | June | 18 | June | 1667 | 1667-52 | 52 | 10 | December | 17 | December | 1667 |