Usually, this behavior is seen if NTP is not properly synced from the source.
If you encounter this issue and you can still access the Server, try to do the following.
1. service ntpd status
2. ntpq -pn
For item 2, please check the delay or jitter that is returned. If it is high, please re-sync your ntp.
3. ntpstat or service ntpd restart
Check again after a few seconds if ntp has synced properly. After that, you can test to run your script. If this does not work, attempt to reboot your Server.