why does 1M differ in number of days(D) with respective to negative sign assigned to it in the prefix?

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Posted on by AXBOY

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Hi All,

i getting the following output :

CalcDate(-1M, Today()) - Today() = 31D ; CalcDate(-1M, Today()): Todays date - 31 D

Today() + CalcDate(+1M, Today()) = 30D ; CalcDate(+1M, Today()): Todays date + 30 D

Why there are days are different with 1M ?

Thanks in Advance

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Daniel Rimmelzwaan 3,485 on at

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RE: why does 1M differ in number of days(D) with respective to negative sign assigned to it in the prefix?

I don't think it works quite that way. When you start on March 30 and you add 4 days (4D) it goes into April so it has an effect on the month too. Same if you start on Wednesday April 29 and you add a week, it goes into May so there's an effect on the month number as well. It depends on the reference date.

Don't try to disassemble the CalcDate command into pieces.

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Teddy Herryanto (Th... 14,169 Super User 2025 Season 2 on at

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RE: why does 1M differ in number of days(D) with respective to negative sign assigned to it in the prefix?

Never actually try it, but I am assuming that is correct.

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AXBOY 607 on at

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RE: why does 1M differ in number of days(D) with respective to negative sign assigned to it in the prefix?

Thank you so much. Also i have few small doubts :

1. M and Q will effect the month part of the date

2. D and W will effect the days part of the date.

right?

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Daniel Rimmelzwaan 3,485 on at

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RE: why does 1M differ in number of days(D) with respective to negative sign assigned to it in the prefix?

No, 1M is not the same as 31D. It basically tries to simply add 1 to the month number, and if the day number is invalid it finds the first available one. So in this case it is March 31, plus one month is April 31 but that's not a valid date so it adjusts to April 30. Most of the time the day number is not adjusted, and the month number simply gets modified.

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Teddy Herryanto (Th... 14,169 Super User 2025 Season 2 on at

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RE: why does 1M differ in number of days(D) with respective to negative sign assigned to it in the prefix?

1M does not add 30 or 31 days. It's adding to the month, not to days.

4/30/2020 + 1M will become 5/30/2020

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AXBOY 607 on at

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RE: why does 1M differ in number of days(D) with respective to negative sign assigned to it in the prefix?

But 1M = 31D right.

So CalcDate(+1M, Today()) , it should add 31 days with currDate .ie 5/1/2020

But its giving me 4/30/2020, it added only 30 Days

Why?

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keoma 32,729 on at

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RE: why does 1M differ in number of days(D) with respective to negative sign assigned to it in the prefix?

march has 31 days, april has 30 days. ;-)

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