A few months ago I was introduced to the new DateTimeOffset type and was glad DateTime's flaws with regard to time zones were finally taken care of.
However, I was left wondering if there were any overhead or problems that could occur from using this new type.
I work on a multi-locale web application. Does anyone know of anything that could sway me from just using it for all my date/time work? Is there a window for abuse here?
Reference: DateTimeOffset: A New DateTime Structure in .NET 3.5 by Justin Van Patten
Sometimes you really just want to represent a "local" (timezone unaware) date and time rather than an instant in time. To be honest it's more often useful to represent just a time - e.g. "wake me up at 8am, regardless of timezone" - but date and time could be useful too.
I agree that for the vast majority of cases, DateTimeOffset is a better fit. It does strike me as odd that there isn't a DateTimeTimeZone struct which has both the instant and its timezone though... an offset doesn't actually give you all the information you need. (For instance, given a DateTimeOffset, you don't know what the time will be 24 hours later, because you don't know when DST might kick in.)
If you want that kind of structure, I have a very crude implementation in another answer. I'm sure it could be improved very easily :)
Well, one obvious answer would be when you need to support clients without the SP that it ships in (it isn't actually in 3.5 - it is in 2.0 SP1, which shipped at the same time).
Whilst I wouldn't PREFER to use DateTime over DateTimeOffset, please note that sometimes you NEED to, as MS .Net does not support DateTimeOffset as a DataColumn.DataType property DataColumn.DataType Property even though SQL datetimeoffset has been around since SQL2008.
I myself had a problem with reading (ReadXml) a DateTimeOffset value of an XML exported DataSet with XmlReadMode.InferTypedSchema; it read it as a DateTime and crashed when I tried to merge it into a DateTimeOffset column
来源：https://stackoverflow.com/questions/264617/when-would-you-prefer-datetime-over-datetimeoffset