Universal Year is the term that describes one "year" in universal terms. In the year 2500 A.D. on Old Earth, a number perfectly divisible by 4, the Universal Year began.
A Universal Year is calculated by taking four years worth of Earth Years and adding the days up. As every year included a quarter of a year, it was only right to include that extra day as part of the Universal Year cycle. Therefore, there are 1,461 days in a Universal Year.
The reason there are 1,461 days in a Universal Year is a customary carryover that reminds everyone where their ancestors came from. 1,461 days are in four Earth Years. One day is comprised of 25 hours (the extra hour was "added" to round off the hours in one day), one hour is comprised of 60 minutes, and 60 minutes are comprised of 60 seconds. The 25th hour is an "extra hour" that occurs after the 12 a.m., a "13 a.m." before the clock resets to "0 a.m." for the next day.
Once the Universal Year was established as the norm for dictating time and age. For example, a person who is five Universal Years of age is twenty years old if you go by Earth Years.
Months were abolished as the official way to describe a section of a Universal Year. Instead the day of the year is simply noted by what number the day actually is, such as "Day 995." Although, some like to calculate which month a certain day would fall on if Earth Years were still in use, and would refer to them by the segment the month fell in, for example "Second January" or "Fourth December." Day 995 would be "Third September 21." There is only one 29th of February, called "First February 29," also known as "Day 1154." To annotate the day in the Universal Year, it is just added on the end of the exact date. For example, "UY 20, Day 995" or "UY 32, Fourth October 12" or if you were speaking aloud "UY 32, the 12th of the Fourth October."
It can get quite complicated when filling out forms and paperwork so there is a more or less standard short-form way to write the exact day. If someone was born on the 400th day of the 3rd Universal Year, it would be written in short-form as "3/400." Depending on the region of the universe you are from, short-form may or may not be used, opting to use the longer forms explained above.