I keep seeing the Additional Tagging and Reporting Tools plug-in suggested in answers to questions like this.
I don't use it, so I just installed it to check it out.
And, well... hot diggity.
I know the plug-in has its fans, but I'll just say anyone that doesn't have Mp3tag in their tagging toolkit for stuff like this is spending a lot more time tagging tracks than they need to.
www.mp3tag.de/en (https://www.mp3tag.de/en)
The best thing about Mp3tag is that you can group a lot of commands into a single Action Group.
So rather than try to construct one massive complicated command or regular expression to do all the work we can break it down into more digestible bite-size pieces.
In Mp3tag, select Actions > Actions to open the Action Groups list (or press Alt+6).
Click the New button (with the little star) to create a new Action Group and give it a meaningful name like "Format Album Date".
Assuming an Album tag in this format:
e.g. 4/15/83 Community War Memorial Auditorium, Rochester, NY
In Mp3tag, the command Format value assigns a value to a field (i.e. tag).
We can use this three times to pick out the parts of the date and save them for later.
Field: TEMPYEAR
Format string: $RegExp(%Album%,'(\d{1,2})\/(\d{1,2})\/(\d{2}) (.*)','$3')
Field: TEMPMONTH
Format string: $RegExp(%Album%,'(\d{1,2})\/(\d{1,2})\/(\d{2}) (.*)','$1')
Field: TEMPDATE
Format string: $RegExp(%Album%,'(\d{1,2})\/(\d{1,2})\/(\d{2}) (.*)','$2')
We can use some the same command with some other functions to prepend the century to years that only have two digits.
As an added bonus we can check the value of two-digit years to set it to the correct century.
Field: TEMPYEAR
Format string: $If($Eql($Len(%TempYear%),2),$IfGreater(%TempYear%,22,19%TempYear%,20%TempYear%),%TempYear%)
(You'd need to update the 22 in that formula each year to keep it current)
Mp3tag has a $Num function that can be used to pad digits with a specified number of zeroes so we can use that for the month and date:
Field: TEMPMONTH
Format string: $Num(%TempMonth%,2)
Field: TEMPDATE
Format string: $Num(%TempDate%,2)
Then we use the Format value command again to set the date using our newly formatted values:
Field: DATE
Format string: %TempYear%-%TempMonth%-%TempDate%
Finally use the Remove fields commands to delete the temporary fields we used to construct the date:
Fields to remove: TempYear;TempMonth;TempDate
Putting all that together as a single Action in Mp3tag will result in this:
(https://i.imgur.com/OIPBS77.png)
Load the tracks from your album into Mp3tag, run that one action, and they will all have their Date field set to 1983-04-15.
Another great time-saver in Mp3tag is a not-so-documented feature for keyboard access.
If you include an ampersand in your action title, that becomes the keyboard shortcut to run that command.
So you could call your action Format Album &Date for example, and then run it by pressing Alt+A, D.
(https://i.imgur.com/6sJWdAu.png)
(The Alt+A is Mp3tag's built-in key for the Actions menu)
An even-less-documented feature is that you can include a hash symbol to group commands into sub-menus.
Call the same action #Format Album &Date#&1. Month-Date-Year, and then run it by pressing Alt+A, D, 1.
(https://i.imgur.com/kCweX7t.png)
This way you could make different versions of the same action for each of the different date formats your albums use and access each one with a different number.
You'll never tag faster than once you've committed those shortcuts to muscle memory.
-edit-
Updated to describe how to create a new Action Group.
Also, I forgot to mention that Mp3tag uses the Action Group title for the configuration file that stores its actions.
So you can't use characters in Action Group titles that would be invalid in a file name. : / ? * etc.