§ 4000.43 How do I compute a time period?

(a) In general. If you are computing a time period to which this part applies, whether you are counting forwards or backwards, the day after (or before) the act, event, or default that begins the period is day one, the next day is day two, and so on. Count all days, including weekends and Federal holidays. However, if the last day you count is a weekend or Federal holiday, extend or shorten the period (whichever benefits you in complying with the time requirement) to the next regular business day. The examples in paragraph (d) of this section illustrate these rules.

(b) When date is designated. In some cases, our regulations designate a specific day as the end of a time period, such as “the last day” of a plan year or “the fifteenth day” of a calendar month. In these cases, you simply use the designated day, together with the weekend and holiday rule of paragraph (a) of this section.