I have a data set that contains variables for economic growth (called "dgdp") and the change of unemployment rate (called "dUR") for a variety of countries over time in yearly increments from 1991 to 2017. Previously, I tested for a break in time series with an unknown break date successfully using the following code:
Code:
    regress dUR dgdp if compldata_dgdp_dUR ==1 & country == "Germany", vce(robust)
    tsset ilo_code year
    estat sbsingle
Now, I would like to perform the test with known break dates, so replacing sbsingle with sbknown, break(possible break date). However, the following code does not work:
Code:
    regress dUR dgdp if compldata_dgdp_dUR ==1 & country == "Germany", vce(robust)
    tsset ilo_code year
    estat sbknown, break(2007)
It keeps giving me the following error message:
. tsset ilo_code year
panel variable: ilo_code (unbalanced)
time variable: year, 1991 to 2017
delta: 1 unit

. estat sbknown, break(2007)
no such variables;
the specified varlist does not identify any testable coefficients
r(111);
I suspect that the problem is the date format, but browsing the STATA documentation, I could not find a way to tell STATA that I would like to test for a break in the year 2007. In my data set, year is an integer variable ranging from 1991 to 2017.

Could you please help? Thank you very much for your time.