The current unix timestamp is:
In human-readable form Y-m-d H:i:s:
Today's unix timestamp is provided above, as well as the human readable, date-version of the same timestamp.
The following table shows how many seconds there is over different time spans. Note that values are only approximates. The actual number of seconds in given periods may very due to leap seconds; in addition, the number of days in a single month also varies. If you need precision, then you should not rely on UNIX timestamps.