= Stata Datetime Pseudo-Functions =

Stata supports these '''datetime pseudo-functions functions''' in the global scope.

<<TableOfContents>>

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== Tc ==

Create a value representing the number of milliseconds since the Stata epoch (`01jan1960 00:00:00.000`).

There are two functions: '''`tc`''' and '''`tC`'''.

To create a datetime that ''ignores'' leap seconds, try `tc(01jan1960 00:00:00.000)`.

To create a datetime that ''includes'' leap seconds since the epoch, try `tC(01jan1960 00:00:00.000)`.



=== Converting SPSS Dates and Datetimes ===

The `tc` pseudo-function can be used to normalize dates and datetimes that are imported from [[SPSS]].

SPSS represents dates ''and'' datetimes are the number of seconds since the SPSS epoch (`14oct1582 00:00:00`), ignoring leap seconds. Therefore, to normalize an SPSS date or datetime, convert seconds to milliseconds and add `tc(14oct1582 00:00)`.

{{{
generate double datetime_stata = (datetime_spss * 1000) + tc(14oct1582 00:00:00)
format datetime_stata %tc
}}}



=== Converting R Datetimes ===

Very similarly, the `tC` pseudo-function can be used to normalize datetimes that are imported from [[R]].

R represents datetimes as the number of UTC-adjusted milliseconds since the Unix epoch (`01jan1970 00:00:00`). Therefore, to normalize an R datetime, subtract `tC(01jan1970 00:00:00)`.

{{{
generate double datetime_stata = datetime_r - tC(01jan1970 00:00:00)
format datetime_stata %tC
}}}

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== Td ==

To create a value representing the number of days since the Stata epoch (`01jan1960 00:00:00.000`), try `td(01jan1960)`.



=== Converting R Datetimes ===

The `td` pseudo-function can be used to normalize dates that are imported from [[R]].

R represents dates as the number of days since the Unix epoch (`01jan1970 00:00:00`). Therefore, to normalize an R date, subtract `td(01jan1970)`.

{{{
generate long date_stata = date_r - td(01jan1970)
format date_stata %td
}}}

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== Th ==

To create a value representing the number of half years since the Stata epoch (`01jan1960 00:00:00.000`), try `th(1960-h1)`.

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== Tm ==

To create a value representing the number of months since the Stata epoch (`01jan1960 00:00:00.000`), try `tm(jan1960)`.

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== Tq ==

To create a value representing the number of quarters since the Stata epoch (`01jan1960 00:00:00.000`), try `tq(1960-q1)`.

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== Tw ==

To create a value representing the number of weeks since the Stata epoch (`01jan1960 00:00:00.000`), try `tw(1960-w1)`.

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== Ty ==

To create a value representing the number of years since the Stata epoch (`01jan1960 00:00:00.000`), try `ty(1960)`.



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