There are no official conventions on Ur-Delth for naming years, months, days or even hourly time. Different regions of the world use their own naming conventions and ways of tracking time.
In general, here is how time passes on Ur-Delth:
Year = 375 days
Day = 23 hours
Most (but not all) intelligent beings further divide the year into months and weeks. Here is the typical division for weeks and months (keep in mind that these divisions are not standard to all beings):
Year = 15 months / 75 weeks
Month = 5 weeks / 25 days
Week = 5 days