About 75% of North Dakota is in the Central Time Zone, while the southwest quarter is in the Mountain Time Zone.
Mountain Time is observed in:
Central Time is observed throughout the rest of the state.
IANA time zone database
In the IANA time zone database, North Dakota is covered by five time zones, columns marked "*" contain the data from the file zone.tab:
References
Time in North Dakota Wikipedia(Text) CC BY-SA