Time used is truncated julian day  and milliseconds of day, often given by 
long array, tjd=[truncated julian day, milliseconds of day] .

Seconds from tjd=[0,0] is also used, often given by double precision floating
variable, sec.

Truncated julian day for SWE data is taken from telemetry. 

Data times that are always kept are both truncated julian date and pb5 time, 
given as long array, [year, day number, millisec of day], 
ex:[1994, 334, 43200000], where jan 1 = day 1.

IMPORTANT! 
1.Truncated julian date time base rolled over to tjd=[0,0] on 
Oct 10, 1995 , pb5=[1995 283 0]. The rollover is taken into account 
in procedure "pb5_tjd.pro" (converts from pb5 to tjd) and 
in procedure "tjd_pb5.pro" (converts from tjd to pb5). 
All conversions to (from) tjd must first be from (to) pb5. 

2. Time differences should be computed using procedure "elapsed_seconds.pro", 
which accounts for the rollover.

Following the above (1. and 2.) will make the tjd rollover transparent 
to the user.

