Yes, time.time() returns the number of seconds since an unspecified epoch. Note that on most systems, this does not include leap seconds, although it is possible to configure your system clock to include them. On cpython, time.time is implemented as a call to the C function time, which per ยง27.23.2.4.2 of the C standard does not have to use a specified epoch:
The
timefunction determines the current calendar time. The encoding of the value is
unspecified.
On virtually every OS (including Linux, Mac OSX, Windows, and all other Unixes), the epoch is 1970-1-1, 00:00 UTC, and on these systems time.time is timezone-independent.