see:
http://spreadsheetpage.com/index.php/tip/converting_unix_timestamps/

Moosimeter time stamps are UTC seconds since Jan 1, 1970. Microsoft Excel will convert directly to UTC MM/DD/YY if you set the column format to “date” (you’ll need to add a correction to get your local time zone), or for other spreadsheets (Open Office) you can use the conversion formula from that web site:

for Open Office:
=(((<timestamp>/60)/60)/24)+DATE(1970;1;1)

aloha.

PS- clearly Mooshimeter does have an RTC..