Calculate two time difference with Linux shell

1, there are two records in the log
ID Start time End time
0dedffee485e7ddbbff1236cfc0d91 2018-06-28 16:55:37 2018-06-28 16:55:52
122dw049dc21b0a7dcdfegeat8c8 2018-06-28 17:21:01 2018-06-28 17:21:23
How can I use the Linux shell command to calculate the number of seconds (end time-start time)?

Get the start and end time strings based on.
start=date +%s -d "2018-06-28 16:55:37"
End=date +%s -d "2018-06-28 16:55:52"
echo $ (($end-$start))

If your log file output format is the above, there are the following methods:
Cat log File | awk '/^000/{
Start=$2 ""
End=$4 ""
Stm=mktime (Gensub (/[:-]/, "", "G", start))
Etm=mktime (Gensub (/[:-]/, "", "G", end))
Print "-" etm-stm
}‘

Calculate two time difference with Linux shell