1. Enter the formula shown below.
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Explanation: ROUNDUP(x,0) always rounds x up to the nearest integer. The MONTH function returns the month number of a date. In this example, the formula reduces to =ROUNDUP(5/3,0), =ROUNDUP(1.666667,0), 2. May is in Quarter 2.
2. Let's see if this formula works for all months.
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Explanation: now it's not difficult to see that the first three values (months) in column B are rounded up to 1 (Quarter 1), the next three values (months) in column B are rounded up to 2 (Quarter 2), etc..