Datepart/Clockpart

[Charlotte Romare]

Hi everyone
In my dataset I have a time variable. It is in format: %tcDay_Mon_DD_HH:MM:SS_CCYY (this is variable “Date”). Storage type float.
According to the ddatetime.pdf I should be able to extract for example year from that variable.
I have tried both:
gen RegYear = clockpart(Date, “year”) and
gen RegYear = datepart(Date, "year")
But both generates an error message (for clockpart): unknown function clockpart() r(133);
What am I doing wrong?
All the best!

[Ken Chui]

Have you tried this?

gen RegYear = year(Date)

[Charlotte Romare]

Thanks for your suggestion. I have tried that but it only generated missing values…

[Nick Cox]

If you have a date-time variable it should be double not float as advised prominently within help datetime

Otherwise I suspect you're reading a help file that is more up-to-date than your Stata. Please let us know if your version is <17 (https://www.statalist.org/forums/help#version).

Ken Chui #2 year() pulls the calendar year out of a daily date but for a date-time variable you need year(dofc())

[William Lisowski]

What version of Stata are you using? The clockpart() function was added in Stata 17.0; if you are using an earlier version it does not exist, and would not be mentioned in the output of help datetime.

The year function mentioned in post #2 only works on SIF date values, so perhaps

gen RegYear = year(dofc(Date))

will do what you seek.

You have a second problem. You tell us your datetime value is storage type float. The output of help datetime tells us that when you convert a string to a Stata Internal Format datetime numeric value, you must create the numeric value as double, not float. Having created your variable Date as float, it is imprecise and this cannot be corrected by converting it from float to double. You must return to your original string and convert it using

generate double Date = clock( ...

[Charlotte Romare]

Thank you so much! This explain why I could not make it work. I have STATA 16… But
gen RegYear = year(dofc(Date)) worked out fine. It also worked out fine to extract weekday using “dow” instead of “year”.
Thanks again!

[Nick Cox]

Worked out fine?

Yes, in that year() and dofc() are supported in Stata 16, and for some versions previously.

No, in that as William Lisowski and I flagged, a datetime variable that is float was probably messed up in detail, so checking results very carefully could be in order,