create timestamp from a given date

Hello,
I am working on my new website which should be populated dynamically by some robots I am writing in java. The robots are supposed to insert posts directly into the database. Iknow what tables need to be modified and how. I use drupal only for displaying the posts to the users (I use drupal for its simplicity, and by the way, drupal is the best product I found for creating a site in few hours).

My question is simple: how can I create the drupal timestamps for the dates (I can have the date in any format, for instance in sql date format).
So, I'm not asking for someone to write the java code which creates the timestamps, I only need to know if there is a function in drupal which does tah so I can translate it in java, or, if there is some documentation which will explain me the format of that timestamp (how to compute it).

Any clue is appreciated,
Thanks,