The date when the participation of the employees of a participating unit may commence shall be at the beginning of the first month of a calendar quarter. Source: SL 1967, ch 303 , § 10; SDCL § 3-12-37; SL 1968, ch 216 , § 1; SL 1974, ch 35 , § 28; SL 2009, ch 20 , § 1; SDCL § 3-12-70 ; SL 2019, ch 22 , § 1.