We have e.g. this constant in C#:
System.Globalization.DateTimeFormatInfo.InvariantInfo.SortableDateTimePattern
It has this value:
"yyyy'-'MM'-'dd'T'HH':'mm':'ss"
I do use it in the ParseExact function and then yyyy-MM-ddTHH:mm:ss works as well.
I cannot figure out what the single quotes are for.
It's a literal string delimiter.
Anything between the single quotes is interpreted as a literal character, and will not be interpreted as a custom format string.
They are equivalent to escaping using a backslash: dd'T'HH is the same as dd\THH.
In your string yyyy'-'MM'-'dd'T'HH':'mm':'ss, the quotes are unnecessary around the - and T, as those are not custom format strings, and so will always be interpreted as string literals. However : is a format specifier, which evaluates to a time separator that's suitable for the current culture. Quoting it as ':' means that the literal character : will always be used, regardless of the current culture.
It's useful to know that this is the same format used by the Windows GetDateFormat function. You use apostrophe's to indicate some literal you want inserted into the resulting string.
More documentation of the string formatting codes can be found on:
In your string it is indiating that it literally wants to add hyphens, colons, and the T characters:
yyyy
'-'MM'-'dd'T'HH':'mm':'ss
In general you don't want to construct dates/times with literally a hyphens (-) or colons (:), or even slashes (/). Because those are wrong for cultures that don't use slashes and colons to construct dates/times:
What you would want to do, if you want to indicate:
Is use the special:
And construct a format such as:
dd/yyyy/MM ss:HH:mm
I don't know what business need one might have to show a date as:
But this way the localizer will insert the culture's correct date and time separators.
Whereas if you literally asked for /, -, or ::
'/' yyyy '/' MM ss ':' HH ':' mmYou will literally get:
rather than: