How do you get a timestamp in JavaScript?

How can I get a timestamp in JavaScript?

Something similar to Unix's timestamp, that is, a single number that represents the current time and date. Either as a number or a string.

datetime vs timestamp?

What would you recommend using between a datetime and a timestamp field, and why? (using mysql). I'm working with php on the server side.

MySQL datetime fields and daylight savings time — how do I reference the "extra' hour?

I'm using the America/New York timezone. In the Fall we "fall back" an hour -- effectively "gaining" one hour at 2am. At the transition point the following happens:

PHP How to find the time elapsed since a date time?

How to find the time elapsed since a date time stamp like 2010-04-28 17:25:43 , final out put text should be like xx Minutes Ago / xx Days Ago