How do I obtain a date variable that shows 1st January of the current year in the format specified in the user's setup?

You can use the following computation:

// calculate number of days since 1st January

Set V[days] "&V[today_d.m.y]"  -   "01.01.&V[today_y]"

// subtract from current date

Set V[jan01]  "&V[today_user]"   -   "&V[days]"