How to convert Date and time into unix timestamp in google sheet

Question

I have a Google Sheet with a datetime string in the following format:

15-08-2021 12:30:00

I want to convert the above into a Unix timestamp, resulting in:

1629012600

Note: I do not want to use Google Apps Script.

Answer 1

(new Date(2021,7,15,12,30,0).valueOf()/1000).toFixed();