And if those systems seem too capricious, mark the passage of time with something more natural, like the calendars nature produces, which are based on recurring physical phenomena. Solar and lunar eclipses, for example, repeat every 18 years and 11.33 days, an interval called a saros. The saros, all 6,581.33 days, is the common denominator of the three periods. Or you could count in terms of three saroses, an interval of 54 years and one month, the time frame in which eclipses return to the same part of the globe. These patterns may not get media attention, but they're reliable.
Astronomers have more than saros periods with which to count.
For starters, they have their own system of days. After all, it's not easy to figure out exactly how much time has elapsed between two events when all manner of irregular months and leap years intervene. So to keep tabs on the uneven pulsations of Orion's swollen star Betelgeuse, now in the southwest at nightfall, an astronomer would count in Julian days. It's not exactly a catchy thing, but if you want to jump on the Julian bandwagon, set your watch to J.D. 2,451,269.0 at noon on April 1. Astronomy lets you choose from almost limitless counting schemes.