A time of 24:00 is a valid in ISO8601 dates.

Midnight is a special case and may be referred to as either "00:00" or "24:00". The notation "00:00" is used at the beginning of a calendar day and is the more frequently used. At the end of a day use "24:00". "2007-04-05T24:00" is the same instant as "2007-04-06T00:00" (see Combined date and time representations below).

https://en.wikipedia.org/wiki/ISO_8601

var dt = DateTimeOffset.Parse("2007-04-05T24:00");
var dt = DateTime.Parse("2007-04-05T24:00");

System.FormatException: 'The DateTime represented by the string '2007-04-05T24:00' is not supported in calendar 'System.Globalization.GregorianCalendar'.'
   at System.DateTimeParse.Parse(ReadOnlySpan`1 s, DateTimeFormatInfo dtfi, DateTimeStyles styles, TimeSpan& offset)
   at System.DateTimeOffset.Parse(String input)
   at ConsoleApp17.Program.Main(String[] args) in C:\Users\James\source\repos\ConsoleApp17\ConsoleApp17\Program.cs:line 10

Should be fixed in DateTimeOffset.Parse/DateTime.Parse and new Utf8Parser API.