To avoid paying the tax on newspaper advertisements, Isaiah Thomas published what previously had been the newspaper Massachusetts Spy as an octavo-size magagine from 11 April 1786 until 27 March 1788. (The newspaper Massachusetts Spy reappeared on 3 April 1788 once the tax was repealed.) The Worcester Magazine was published on Thursdays and was dated only by the week and month of the year. The following table converts the week and month dating to an actual date. The actual dates were used in all four Massachusetts volumes and Mfm:Mass.
1787
| 1st Week in August | 9 August |
| 2nd Week in August | 16 August |
| 3rd Week in August | 23 August |
| 4th Week in August | 30 August |
| 1st Week in September | 6 September |
| 2nd Week in September | 13 September |
| 3rd Week in September | 20 September |
| 4th Week in September | 27 September |
| 1st Week in October | 4 October |
| 2nd Week in October | 11 October |
| 3rd Week in October | 18 October |
| 4th Week in October | 25 October |
| Last Week in October | 1 November |
| 1st Week in November | 8 November |
| 2nd Week in November | 15 November |
| 3rd Week in November | 22 November |
| 4th Week in November | 29 November |
| 1st Week in December | 6 December |
| 2nd Week in December | 13 December |
| 3rd Week in December | 20 December |
| 4th Week in December | 27 December |
1788
| 1st Week in January | 3 January |
| 2nd Week in January | 10 January |
| 3rd Week in January | 17 January |
| 4th Week in January | 24 January |
| Last Week in January | 31 January |
| 1st Week in February | 7 February |
| 2nd Week in February | 14 February |
| 3rd Week in February | 21 February |
| 4th Week in February | 28 February |
| 1st Week in March | 6 March |
| 2nd Week in March | 13 March |
| 3rd Week in March | 20 March |
| 4th Week in March | 27 March |