Time measurements Millennium . A millennium was a period of one thousand years . In 2000 , Henry Janeway expressed his belief that he ' d been born in the wrong millennium . ( ) Century . A century was a period of one hundred rotations around the sun . Human and Vulcan centuries were " not " equivalent to Lactran centuries . ( ) Decade . A decade was a period of ten years . " According to in the mirror universe , a Human lost a decade off their life expectancy for every year spent working near a warp core . " ( ) Year . A year was the amount of time it took for a planet to orbit its sun . If the planet had an axial tilt , this resulted in seasons , like winter , spring , summer , and fall . Standard UFP solar year . Standard UFP solar years were mentioned in the Treaty of Armens . ( , " okudagram " ) Earth year . One Earth year was equal to 365 . 2425 Earth days in the Gregorian calendar . To compensate for the fraction of a day , a leap day was added to every year whose number was divisible by four , unless it was a century , unless it was divisible by 400 . These leap years consisted of adding an extra day to the month of February . Instead of the usual 28 days , there would be 29 . Scientists usually used a Julian year of 365 . 25 days for measurements and scientific comparisons . According to Doctor Phlox , Travis Mayweather was twenty - six Earth years during his autopsy in 2152 . ( ) Month . A month was usually the amount of time it took for a moon to orbit its planet . This was usually a portion of a year , and a large number of days ( in which case it may be broken down into weeks ) . On Earth a month was originally the length of the lunar cycle ( 29 . 53 days ) . Most calendars at some point made the month one twelfth of a solar year ( 30 . 44 days ) . In Earth ' s most common calendar , the months are either 30 or 31 days long , with one shorter month ( February ) having 28 or 29 days depending on the year . On an uninhabited planet it only gets night four days a month due to its binary stars . ( ) Week . A week was small number days grouped together as part of a calendar system . It could be a portion of a month or an unrelated grouping . On Earth a week was seven days . Takret only needed to sleep once a week . ( ) Travis Mayweather and his father once took shelter in the ship ' s core to protect against a class 3 neutronic storm . They were there for six weeks . ( ) Day . A day was the amount of time it takes for a planet to spin once on its own axis . This resulted in a day / night cycle ( with day in this second case meaning the sunlit portion of the full day ) . On Earth , a full day was divided up into twenty - four hours , whereas on Deep Space 9 , a full day was divided into twenty - six hours . ( ) On an uninhabited planet that explored in 2152 , night was only available on four days a month due to the planet ' s binary stars . ( ) " In 2263 of the alternate reality , Captain told Doctor , shortly after Kirk returned from an unsuccessful away mission to the planet Teenax , that it was " just another day in the fleet . " Kirk subsequently made a log entry in which he reported that the " Enterprise " was on its 966th day in deep space , and that telling where one day ended and the next one began was increasingly difficult . This was around a couple of days before his thirtieth birthday . " ( ) A day was divided into time units including morning , afternoon , evening , and night . Midnight was a specific time on a day . ( ; ; ) Standard UFP solar day . Standard UFP solar days were mentioned in the Treaty of Armens . ( , " okudagram " ) Hour . An hour was a portion of a day , this could be a decimal tenth of a day , or some other fractional portion of a day . On Earth an hour was an SI unit of time that was approximately 1 / 24 of a day , and was divided up into 60 minutes . A shapeshifter had to regenerate after sixteen hours in solid form . ( ) Minute . A minute was a portion of an hour , this could be a decimal hundredth of an hour , or some other fractional portion of an hour . On Earth a minute was 1 / 60 of an hour , and was divided up into 60 seconds . In colloquial speech , a minute can also mean an undefined short amount of time , as in " " I ' ll be just a minute " " . ( ) The crew of would be dead within three minutes when exposed to the radiolytic isotope s of a neutronic storm . ( ) Second . A second was a portion of a minute , this could be a decimal hundredth of a minute , or some other fractional portion of a minute . On Earth a second was 1 / 60 of a minute , and was usually divided up decimally . Taking a neural toxin would kill the Denobulan Phlox in only a few seconds . ( ) Nanosecond . A nanosecond was one billionth of a second . In 2365 , the was destroyed by a plasma vent that lasted T + 2 . 25 nanoseconds . ( ) To attract the attention of the Crystalline Entity , the emitted five - nanosecond graviton emission s at one pulse per second . ( ) Stardate . Main article : Stardate In the 23rd century , stardates were not directly related to Earth ' s calendar . Beginning in 2323 , stardates were changed to be 1 , 000 per Earth year .