Wrong magic number for 2019/01/01 about mavproxy

[shancock884]

I agree, the number in the code looks wrong.
One thought: if you put the call to datetime into the timestamp_2019 function, then Python will end up re-running the code to recalculate this constant value every time it is called.
So maybe calculate it in __init__ so that its only done once, or hard code the right value with a suitable comment about how you got it.

Also, from unix epoch of 1st Jan 1970, the maths could be also be done without time functions, something like this:
3600*24*int(365.25*(2019-1970))
Or more generically (valid between 1901 and 2100):

def unix_time_1_jan(year):
    3600*24*(365*(year-1970) + math.floor((year-1969)/4))