29 C.F.R. § 2530.200b-3
(c) Use of equivalencies for determining service to be credited to employees.
(3) For purposes of this section:
(5) Examples.
(e) Equivalencies based on periods of employment.
(1) Except as provided in paragraphs (e)(4) and (6) of this section, a plan may determine the number of hours of service to be credited to employees in a computation period on the following bases:
(3) Examples. The following examples illustrate the application of paragraphs (e)(1) and (2) of this section;
(7) A plan may combine an equivalency based on working time permitted under paragraph (d) of this section (i.e., hours worked or regular time hours) with an equivalency based on periods of employment permitted under this paragraph if the following conditions are met:
(f) Equivalencies based on earnings.
(1) In the case of an employee whose compensation is determined on the basis of an hourly rate, a plan may determine the number of hours to be credited the employee in a computation period on the basis of earnings, if:
(ii) 870 hours credited under paragraph (f)(1)(i) of this section are treated as equivalent to 1,000 hours of service, and 435 hours credited under paragraph (f)(1)(i) of this section are treated as equivalent to 500 hours of service.
For purposes of this paragraph (f)(1), a plan may divide earnings at premium rates for overtime by the employee's hourly rate for overtime, rather than the regular time hourly rate.
(2) In the case of an employee whose compensation is determined on a basis other than an hourly rate, a plan may determine the number of hours to be credited to the employee in a computation period on the basis of earnings if:
(3) For purposes of paragraph (f)(2) of this section, an employee's hourly rate of compensation shall be determined as follows:
(4) Examples.