Hello Gerardo,
I don't know how you converted your times but at the page I referenced there's a dropdown list where you can choose between GMT and Local time. As the Unix timestamp is always assumed to be UTC/GMT, you need to convert your Human dates using the GMT option. For example:
If I convert my current local time (11:40 AM GMT-5) using the GMT option, I get the following:
Epoch timestamp: 1411749600
Timestamp in milliseconds: 1411749600000
Human time (GMT): Fri, 26 Sep 2014 16:40:00 GMT
Human time (your time zone): 9/26/2014 11:40:00 AM
But if I convert it using Local time, then I get:
Epoch timestamp: 1411767600
Timestamp in milliseconds: 1411767600000
Human time (your time zone): 9/26/2014 4:40:00 PM
Human time (GMT): Fri, 26 Sep 2014 21:40:00 GMT
As you can see, the timestamp value is quite different (five hours, given my timezone: GMT-5).
So, you only need to make sure that the time settings of your computer are correct and select the GMT option during the Human date/Unix timestamp conversion.
--- Reference
http://www.epochconverter.com
What is epoch time?
The Unix epoch (or Unix time or POSIX time or Unix timestamp) is the number of seconds that have elapsed since January 1, 1970 (midnight UTC/GMT)