Compare Unix date and time

Compare Unix date and time.

To get Unix time, the command is:

current time:

now=`date +"%T"`

we will get a time like "20:55:01"

now=`date +"%H%M%S"`

we will get a time like "205501"

If we want to compare times, we can not compare the times in the format "%H:%M:%S", we can only compare them in the format "%H%M%S". Otherwise we will get an error Illegal number: 20:59:22

To get Unix date, the command is:

date1=`date +"%m/%d/%Y %H:%M:%S"`

We will get a date in like "5/8/2018 20:55:01"

If we want to get timestamp, we will use:

date2=`date +"%s"`

we will get a unix timestamp.

we can compare dates by its unix timestamp. it seems we can not compare two dates like "5/8/2018 20:55:01".  Otherwise we will get an error: Illegal number: 05/08/2018 20:59:22.