Which months were added to the calendar and why?
In order for the Roman calendar year which was ten months long, to be in sync with the lunar year, the months of January and February were added.
Below is an instruction that describes a task, paired with an input that provides further context. Write a response that appropriately completes the request.
### Instruction: Which months were added to the calendar and why?
### Input: 
### Response: In order for the Roman calendar year which was ten months long, to be in sync with the lunar year, the months of January and February were added.