I remember reading in the comments of a Rails blog something along these
"Since a Model is loaded only once in production development (at server
start), certain time-dependent 'constants' that you have placed in a
method of a Model will always return the same value for those
'constants', i.e. the value the 'constant' had at server start."
Hypothetic example for the MySQL 'constant' "UTC_TIMESTAMP()" in a Model