Format of date not executing

[Bill Avant]

Does anyone have a thought of why Calc would stop formatting dates? example. A date column with the format of "year/month/day". I use to enter the date as "month/day/year" and the formatted cell would display the correct format yr/mo/day. Now it doesn't. I don't know if I changed something in options by accident.
I'm using Calc 4.1.3. windows 10,

[RoryOF]

Have you recently updated to Win10 from an earlier Windows?

[Bill Avant]

Have you recently updated to Win10 from an earlier Windows?

It's been sometime ago. However, I don't remember if there has been a recent update

[acknak]

The most common cause of cell/number formats not working is that the cell holds a text value instead of a number. The simplest way to check is with View > Value Highlighting: ON. If the value is displayed in black text, it's text; in blue, it's a number.

[Bill Avant]

The most common cause of cell/number formats not working is that the cell holds a text value instead of a number. The simplest way to check is with View > Value Highlighting: ON. If the value is displayed in black text, it's text; in blue, it's a number.

Ok did that and cells were blue. Thank you. is there another solution, please? I learned a new check technique with your answer, I wasn't aware of.

[Villeroy]

Whenever you enter dates into spreadsheet cells (Excel, Calc, Gnumeric, whatever):
11/ enters this month's 11th da.
11/12 enters this year's 12th of November or in US locale context 11th of December
11/12/13 enters a day/month/year or month/day/year respectively.
In any locale context you can enter ISO dates 2013-12-11.

These are the input patterns that are recognized by any spreadsheet program regardless of the cell formatting.
You can simple enter 3/ and the cell shows "Thursday, August 3 in the year 2017" if the cell is formatted like that

[Bill Avant]

Whenever you enter dates into spreadsheet cells (Excel, Calc, Gnumeric, whatever):
11/ enters this month's 11th da.
11/12 enters this year's 12th of November or in US locale context 11th of December
11/12/13 enters a day/month/year or month/day/year respectively.
In any locale context you can enter ISO dates 2013-12-11.

These are the input patterns that are recognized by any spreadsheet program regardless of the cell formatting.
You can simple enter 3/ and the cell shows "Thursday, August 3 in the year 2017" if the cell is formatted like that

[Bill Avant]

Have you recently updated to Win10 from an earlier Windows?

Rory, yes I went to windows 10 64 bit from win8 32 bit around 10-2016, I think. I was having this problem. no fix. then went from 4g to 8g ram. no fix. however I opened an earlier version of this spreadsheet that actually is larger than this one and it works great. Problem is I have had to add additional sheets. so I removed them on the newer version. now it still doesn't work.
My System is: Edition Windows 10 Pro, Version 1703, OS Build 15063.540, Processor Intel Core i3 CPU 540@3.07GHz 3.06GHz, Installed RAM 8.00GB(7.80GB usable), System Type 64 bit operating System, x64-based processor.
The Calc is 32 bit

[Villeroy]

Does anyone have a thought of why Calc would stop formatting dates? example. A date column with the format of "year/month/day". I use to enter the date as "month/day/year" and the formatted cell would display the correct format yr/mo/day.

If M/D/Y is the right input pattern or not depends on the locale setting in Tools>Options>LangaugeSettings>Languages (2nd item on that options page).
If this option is set to "English (USA)", 1/2 enters 2nd of January and 19/2 is not recognized as date.
You can override this setting for the current spreadsheet document with a modified "Default" cell style (F11, right-click "Default"). Apply number format "General" with explicit "English (USA)" language. Now it may be set to "Default: English(USA)" which means that English(USA) inherits from the global setting and that setting inherits from the system locale.