We can use below to check the clock/time synchronization between nodes in RAC cluster. The crs alert log will also point out thee synchronization issue between the nodes.
Script:

 cd $GRID_HOME/bin 
./cluvfy comp clocksync -n all

 Output:

 Verifying Clock Synchronization across the cluster nodes
Oracle Clusterware is installed on all nodes.
CTSS resource check passed
Query of CTSS for time offset passed

 CTSS is in Observer state. Switching over to clock synchronization checks using NTP
Starting Clock synchronization checks using Network Time Protocol(NTP)...
NTP configuration file "/etc/ntp.conf" existence check passed
Liveness check passed for "ntpd"
Check for NTP daemon or service alive passed on all nodes
Check of common NTP Time Server passed
Clock time offset check passed

 Clock synchronization check using Network Time Protocol(NTP) passed
Oracle Cluster Time Synchronization Services check passed

 Verification of Clock Synchronization across the cluster nodes was successful.

Check whether ctss or ntp is running

 crsctl check ctss 

 CRS-4700: The Cluster Time Synchronization Service is in Observer mode.
Observer means – Time sync between nodes are taken care by NTP

Active means – Time sync between nodes are taken care by CTSS