Is a public employee entitled to a pension when they retire?

"A public employee's pension constitutes an element of compensation, and a vested contractual right to pension benefits accrues upon acceptance of employment. Such a pension right may not be destroyed, once vested, without impairing a contractual obligation of the employing public entity. [Citation.]" (Betts v. Board of Administration (1978) 21 Cal.3d 859, 863.) Before retirement, the employee does not have "any absolute right to fixed or specific benefits, but only to a 'substantial or reasonable pension.'" (Ibid.)