While editing/tagging a question, I noticed that the tag has this info:

for questions specific to data types that contain both date and time parts.

which seems wrong to me. Seeing a "datetime" tag, I would assume the question has to do with "date or time", not "date and time".

So I suggest we merge the 3 tags. I don't think we need 3 separate tags, one for each type, for several reasons:

  • DBMS have sections in their documentation about "Date/Time types" and "Date/Time functions and operators".

  • The two parts (date and time) are related as they exist as separate types and parts of combined types (datetime, timestamp).

  • Questions about a specific type (eg. question specifically about date type are rare and I can't see how tagging with date will be more help than tagging with datetime.

  • Some DBMS (call me Oracle) have no pure date type and they call the datetime type date. Which tag should Oracle users use?
    Or have a tag for each type and dbms: , , , etc? (No, I wouldn't like that)

has 175 questions, has 98 and has 45
(and some of them are common, 15 for example are tagged with both date and datetime).

Are the three tags similar enough to be merged?

Or is there any important difference between them from a tagging perspective?

If you think the tags are different, please add your reasoning to the 'No' CW answer below.

If you agree the tags should be merged, vote 'Yes'.

Additional discussion regarding and tags about non-standard non-standard types like

  • Not sure about , and whether it should be merged or not (shall we have a separate meta question?)

  • is very rare (only 2 questions) and vendor specific, so it could be independently merged into or not. It doesn't matter much.

  • Cool, but I'm still unclear how you think datetime should be used (its guidance). Should the merge target be datetime or date-time? Also, how do you feel about timestamp and datetime2 continuing separately? Feel free to ignore the last part if it is simply out of scope.
    – Paul White Mod
    Dec 24, 2016 at 0:48
  • 2
    I don't know, Paul already mentioned datetime2 but more specifically I would feel weird asking a question about the date data type specifically and having to use the datetime tag.
    – Aaron Bertrand Staff
    Dec 24, 2016 at 5:04
  • I have the opposite feeling but not very strong views, that's why I posted on meta. About datetime2, there are exactly 2 questions tagged with it. Isn't the datetime tag enough to handle those questions, too? Dec 24, 2016 at 10:24

2 Answers 2


No, the 3 tags , and should remain separate.

  • They're discrete types under the hood, and at least in PostgreSQL often functions accept one type and not the other. For instance, I just recently asked this question which has to do with time to the exclusion of date internal and external. That said, I don't much care about this. So while I am voting to keep them seperate, I feel less passionately about this then other things we've disagreed upon. I prefer tags to be more meaningful, even if it takes more skill to use them properly. Dec 24, 2016 at 1:13
  • @Evan I'm not talking about the types but about the tags. I've added some explanation in the question why I think we only need one tag, for the 3+ different types. Dec 24, 2016 at 10:55

Yes, and should be synonyms of and merged.

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