gray78,
anotherhiggins makes an excellent point. However, we all understand "Bosses." Enough said.
You can find the current month using =month(today()). Or use the formula =DATE(YEAR(TODAY()),MONTH(TODAY()),1) in the first worksheet which will obtain the first day of the current month.
However, it would be best for you to place the date of the first of the month into a particular cell on the first worksheet. Then the other worksheets in succession could have a cell that adds one to the cell with the date of the previous worksheet. After the initial setup of all 31 sheets they would all have the appropriate date. The advantage of this is that you could copy the workbook and need to only change one cell on one worksheet for the new month.
Hope this helps.