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convert decimal number resulting from timevalue function back into a time

In Numbers 10, on my Mac or iPhone...

when I use the TIMEVALUE() function, I get the expected "decimal fraction of a 24‑hour day".


TIMEVALUE("6/30/2020 21:00:00") returns 0.875


How do I convert a "decimal fraction of a 24‑hour day" back into the corresponding time, 21:00:00?

Posted on Jul 26, 2020 7:36 PM

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Question marked as Top-ranking reply

Posted on Jul 26, 2020 7:56 PM

There is no "time" without a date. To convert the decimal fraction of a 24 hr day back into a Date&Time value using today as the date,


=TODAY()+.875


TODAY gives todays date at 12:00:00AM. That is the default time when you create a date in Numbers, whether you use the TODAY function or create one some other way (except for NOW which includes the current time).


This also works:

="7/20/2020"+.875

6 replies
Question marked as Top-ranking reply

Jul 26, 2020 7:56 PM in response to iGuy3

There is no "time" without a date. To convert the decimal fraction of a 24 hr day back into a Date&Time value using today as the date,


=TODAY()+.875


TODAY gives todays date at 12:00:00AM. That is the default time when you create a date in Numbers, whether you use the TODAY function or create one some other way (except for NOW which includes the current time).


This also works:

="7/20/2020"+.875

Jul 28, 2020 10:41 PM in response to iGuy3

Hi Guy,


Try this:


Column A contains a set of numbers corresponding to the days of the month being averaged. These are for the user's convenience, and play no part in which calculates the average of the TIMEVALUES calculations.


Column B contains a list of Date and time values, entered as Times at bed time each nght. Numbers will set the date part of the date and time values to the date on which the entry is made, but, as with the numbers in column A, these dates do not enter into the calculations.


Column C contains the formula sown below the table, entered in C2 and filled down to the rest of the cells in that column.

C2: IF(TIMEVALUE(B2)<0.5,TIMEVALUE(B2),TIMEVALUE(B2)−1)


IF the time part of the value i column B is in the AM range, the TMEVALUE will be less than 0.5, and the formula will place that TIMEVALUE in the cell containing the formula. IF the time isin the PM range, the formula will subtract 1 from that TIMEVALUE (resulting in a negative value) and place that result in the cell.


D2 contains this formula:

D2: AVERAGE(C)

This calculates the AVERAGE of the TIMEVALUEs calculated in column C.


D3 contains this formula:

D3: TODAY()+D2

This returns a date&time value of today's date at the time of day indicated by the average TIMEVALUE in D2.

The cell is formatted for date & time, with only the Time part displayed.


As written, the AVERAGE formula may return a false average when not all dates in the month have entries. Wrapping the C2 formula (shown in bold below) with the 'switch' (shown in normal type weight) prevents the calculation when column B is empty, and places a null string ( "" ) in the cell. This text value is ignored by AVERAGE, so the value in D3 is the correct average bedtime for the dates so far recorded in the table.


C2: IF(LEN(B2)<1,"",IF(TIMEVALUE(B2)<0.5,TIMEVALUE(B2),TIMEVALUE(B2)−1))



Regards,

Barry


PS: In the example the time entries in the yellow block of cells are repeated in the rest of column B. Less typing that way.

B.

Jul 31, 2020 9:50 AM in response to iGuy3

iGuy3 wrote:

I’m still wrestling with trying to get a monthly average of my bedtimes. Works fine if I always go to bed after midnight. But, when I hit the sack at 10 PM once, and after midnight every other night, the resulting month average looks incorrect.


You can try something like this:





SG

Jul 28, 2020 4:08 PM in response to Badunit

Thanks for clarifying. I have a hard time wrapping my thoughts around the need to include a date.


I’m still wrestling with trying to get a monthly average of my bedtimes. Works fine if I always go to bed after midnight. But, when I hit the sack at 10 PM once, and after midnight every other night, the resulting month average looks incorrect.

Jul 29, 2020 6:14 AM in response to Badunit

Here is maybe one way to do it that is more universal. Starting with your table with the Date&Time values in column B,


Column C =TIMEVALUE(B)

Column D =IF(C>0.5,C−1,C)

The average time, with today's date attached, would be

=TODAY()+IF(STDEV(C)<STDEV(D),AVERAGE(C),AVERAGE(D))


I cannot say for sure if this works for every case. Averaging values that go around in a circle requires some interpretation. The average of 11PM and 1AM could be equal to 12AM or 12PM; either is a correct answer numerically. I tried to use the standard deviation to bend the answer toward the smaller arc of the circle.

convert decimal number resulting from timevalue function back into a time

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