It is not always possible to get the precise date of an event. There are places and time periods where just determining the year of birth can be a challenge and researchers may only be able to get a range of years for a birth, marriage, or death.
During these times, having a year or a short range of events may be sufficient to help you research the person’s children, spouse, and parents. The key is to make certain that you have looked at all available records and that you have not inadvertently merged two distinct people into one individual.
Always make certain you have exhausted all extant records, but realize that in Virginia in the 1600s, the chance you find a precise date of birth is relatively slim. In Massachusetts in 1600 the chance is significantly higher.
Don’t fret too much if you cannot get a precise date for an event. Remember the key is to narrow the date as best you can, work to establish relationships, document your reasoning, and make certain you have used all available records.