I used it to create the following tables (Figures 2 and 3) of Spring and Fall DST dates, which agree with a similar online table. The same logic can be used to give us the Fall DST date by substituting in the lastest possible first Sunday in November: DATE(2021, 11, 7) - (WEEKDAY(DATE(2021,11,7)-1) =. offset = WEEKDAY(latest) - 1 (Sunday = 0, Monday = 1, …, Saturday = 6).This is simply the weekday number of 14-March-2021 minus 1.Compute the weekday of 14-March-2021 from the previous Sunday.Excel Calculation: latest = DATE(2021, 3, 14).If March 1 st is a Monday, the second Sunday in March is on the 14 th.Create a date object for the latest possible spring DST date (14-March-2021).I will illustrate the calculation using the 2021 Spring DST date calculation. WEEKDAY(date object) This function takes a date object and computes an integer that corresponds to the day of the week, where the default numbering is Monday = 1, Tuesday = 2, …, Sunday = 7. DATE(year, month, date) This function computes an Excel date object, which is an integer equal to the number of days since January 1st, 1900. Solving this problem requires two Excel date functions. The 2005 Energy Policy Act defined the dates of DST to be: I only need to calculate the DST correction for dates after 2005, so I will not worry about earlier years. As discussed below, the US adopted its current DST assignments in 2005. To perform this correction, I need to know if the date/time values occurred during the DST date ranges for those years. My customer only works in Excel, so the work was done in Excel. Because of DST, this is not always the case. To be specific, some transactions from China were recorded assuming a fixed time offset with respect to US Central Standard Time. I recently had a situation where I needed to correct a number of date/time values because they did not take into account Daylight Saving Time ( DST). The clocks change at 2 AM Sunday morning. Figure 1: US Daylight Saving Time Rule: Spring Ahead, Fall Back.
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