Sorry, no.
Fill in UDT0 with 1/1/$Now.Year. 0:00:00 (midnight Jan 1 of current year)
DT2EPOC UDT0 to D100
MATH D101 (DST21 - D100) / (24 * 3600) // D101 contains number of full days since Jan1; add 1 if you want it to truncate up, i.e Jan 1 you want 1, not 0