Dates are an important piece of doing genealogy. You will be coming across dates for all types of historical events, from births and deaths, to immigrations and naturalizations, to land purchases and sales. Each date you will come across in genealogy will have its own importance to your research, and so you will want to ensure you record them accurately.
There are many ways to write a date, depending on where you reside in the world, or your personal preference. In genealogy, there is a standard rule of thumb for writing dates. You should always format your dates by day, month (no abbreviations), and four-digit year: 01 March 1840. If you were to write 03/01/40, someone else may not know if you meant March 1st or January 1st, or 1740, 1840, 1940, or some other year ending in ‘40’. Now why we put the day before the month is a mystery to me, quite honestly. Perhaps it is because this is how most other counties format their dates.
Sometimes you may come across different dates for the same event. In these cases, you should note the discrepancy. You could write something like: 01 March 1840/1, which would mean the event took place in either 1840 or 1841. You could also write one date, making a note underneath about the alternative date. Either way, be sure that both dates are recorded.
It is also common that you may not find the exact date of an event, but you will have an approximate date. For example, you may find Uncle John and Aunt Mary on the 1920 census, and then Uncle John is missing from the 1930 census, while Aunt Mary is listed as ‘widowed”. You can safely assume Uncle John died between 1920 and 1930. Or you can estimate births of siblings based on the idea that children were often born two years apart (this according to studies of many seventeenth and eighteenth century families). To approximate dates, use the formats listed below:
Between: Bet. [DATE] and [DATE]
About (Circa): ca. [DATE]
Before: Bef. [DATE]
After: Aft. [DATE]