You have two possible approaches that I can think of. The first is the fill handle:

- In cell A1, enter 1/23/2013.
- In cell A2, enter 2/23/2013.
- Highlight cells A1 and A2.
- Place your mouse on the fill handle at the bottom right of the group of highlighted cells, and drag down for as many values as you need.

The second, as discussed already, is formulas, but you need to account for the month of December:

```
=IF(MONTH($A1) = 12, DATE($A1 + 1, 1, DAY($A1)), DATE(YEAR($A1), MONTH($A1) + 1, DAY($A1)))
```

- If the month is December, compose a new date,
`DATE()`

, with the following values:
- The original year incremented by 1.
- The month of January.
- The original day of the month.

- Else compose a new date,
`DATE()`

, with the following values:
- The original year.
- The original month incremented by 1.
- The original day of the month.

Note that you still need to validate the day of the month. For instance, January 31 is a valid date, but February 31 wouldn't be. That would be a little more complicated, however, and depends on whether you want to cover every edge case.