Stephen Greb and Brandon Nutall, Kentucky Geological Survey
Calculating/converting geologic ages onto a calendar year
(6) To calculate the calendar time for a geologic event or ancient creature on a full calendar year there are two calculations depending on which way you want to determine dates of the year:(6a) Calculating from the beginning of the calendar year. <make link>
(6b) Calculating from the end of the calendar year. <make link>
There are advantages and disadvantages to both. Since much of the interesting events in geologic time are going to happen at the end of the year, it might be easier to calculate backwards from New Years. However, its easy to be a day off, when you calculate number of days plus some remainder days. For example, 8.5 days from the end of the year, is 8 and a half days from the end of the year, so half way through the 9 th day of the end of the year. Its easy to get confused and think it would be on the 8 th day. In contrast, counting forward from the beginning of the year eliminates the problem of remembering to count partial days, but for most of the days you'll calculate, you'll be in the 300's. A monthly cumulative days of the year chart is shown to help with determining the month and day of the year.