Compute date from shadowExpire in xquery

You can get the shadowExpire value from the 8th field of next command result:

$ getent shadow yourlgin
yourlgin:*::::::17590:0
$ date --date="@$((17590*86400))"
mercredi 28 février 2018, 01:00:00 (UTC+0100)

or convert given value using this simple query:

datetime:timestamp-to-datetime( 17590*86400*1000 )

In the other side:

xs:integer(datetime:timestamp(current-dateTime()) div 86400000)