There are 5 Raspberry Pi's connected to one switch (No Internet) using LAN cables. One of the Raspberry Pi has RTC module connected and it has correct date and time. Now how can all remaining four RPi's can get time and date from that Raspberry Pi?
You could setup a NTP server - there are tutorials describing how to do this, although this requires an understanding of NTP. The clients need to be configured to use the local NTP server in
/etc/ntp.conf (Jessie) or
A much simpler solution is to copy the date from the host (which I use when no network is available).
This can be done manually over
ssh by running
ssh firstname.lastname@example.org sudo date -s$(date -Ins)
This could be automated using cron to run on a regular basis, but the clock in the Pi should be stable enough for most purposes for days/weeks.