Question: how to calculate number of days between two dates in unix?
Answer: Provide valid time string in A and B. Use date -d to handle time strings. Use date %s to convert time strings to seconds since 1970 (unix epoche) Use bash parameter expansion to subtract seconds. divide by seconds per day (86400=60*60*24) to get difference as days. ! DST is not taken into account ! See this answer at unix.