Plaintiff Reinelt appeals from a circuit court affirmance of a decision by defendant Michigan Public School Employees’ Retirement Board denying plaintiff additional military service credit in the computation of plaintiff’s retirement benefits. We reverse.
Plaintiff left his employment as a school teacher to enlist in the Navy on August 21, 1942. Upon enlistment, plaintiff was placed in the Navy’s V-7 program, under which he attended Michigan State Normal College at his own expense, taking courses to prepare him to become an officer. At that time he had a military serial number, rank, commanding officer, and was exempt from military draft. However, he was not paid by the Navy, not required to wear a uniform, did not live in Navy barracks, and did not receive a housing subsidy. On March 9, 1943, he entered active duty in the Navy. Plaintiff’s active duty ended March 28, 1946, and he immediately resumed teaching in Michigan schools. Plaintiff retired July 1, 1974.
In computing plaintiff’s retirement benefits, de*772fendant allowed military service credit only for the period of March 9, 1943, to March 28, 1946.
At the time of plaintiff’s retirement, 1972 PA 170; MCL 38.214; MSA 15.893(14), provided in part:
"A member of this retirement system who was or shall be drafted, enlisted, inducted, or commissioned into military, naval, marine or other armed service of the United States government during time of war or emergency, or who shall be drafted or called into such armed service or emergency during time of peace, and within 24 months from the date of his honorable discharge or relief from active duty from such armed service shall resume employment as a public school employee, shall receive a maximum of 6 years of credit, except required service extending beyond 6 years, for time spent in such armed service credited to him as a member of the retirement system.”
The statute is ambiguous as to how "time spent in such armed service” shall be calculated. Plaintiff argues that the time period starts to run as of the time of draft or enlistment. Defendant argues that the reference in the statute to "relief from active duty” implies that only time spent on active duty is "time spent in such armed service”.
The precise issue raised in this case was addressed by the Attorney General in a letter opinion to Norvel A. Hansen, Executive Director of the Michigan Public School Employees’ Retirement System, dated February 3, 1975. In that opinion the Attorney General reasoned:
"A member of the Public School Employees Retirement System cannot earn service credit pursuant to MCLA 38.214; MSA 15.893(14) unless he or she returns to public school employment 'within 24 months from the date of his honorable discharge or relief from active *773duty from such armed service.’ Thus, a member is not entitled to such service credit until he or she first enters, and then honorably leaves, active duty in the armed services.
"Further, MCLA 38.214; MSA 15.893(14) grants service credit only 'for time spent in such armed service.’ Since such 'time’ ends when the member is honorably discharged from active duty, it must, to be consistent, begin when the member enters active duty.
"It is, therefore my opinion that a member is not entitled to military service credit under MCLA 38.214; MSA 15.893(14) until he or she enters active duty in the Armed Forces.”
The statute was subsequently amended to provide in part:
"A member of this retirement system who was or shall be drafted, enlisted, inducted, or commissioned into active duty with the military, naval, marine, or other armed service * * * .” 1976 PA 357; MCL 38.214; MSA 15.893(14). (Emphasis supplied.)
This amendment appears to have been intended to clear up the instant ambiguity by adopting the Attorney General’s interpretation and expressing that meaning with clarity.
Defendant asserts that this Court must give great weight to the Attorney General’s administrative interpretation of the statute. See, e.g., Magreta v Ambassador Steel Co (On Rehearing), 380 Mich 513, 519; 158 NW2d 473, 475 (1968). It is true that
" '[t]he construction given to a statute by those charged with the duty of executing it is always entitled to the most respectful consideration and ought not to be overruled without cogent reasons.’ ” Magreta v Ambassador Steel Co, supra, quoting United States v Moore, 95 US 760, 763; 24 L Ed 588, 589 (1877).
*774The rationale for this rule is that administrative agencies generally have special competence in interpreting and applying specialized legislation in their field of expertise. See 2A Sutherland, Statutory Construction (4th ed), § 49.05, pp 238, 239. Since the instant interpretation comes not from the agency charged with the duty of executing the statute, defendant board, but from the Attorney General, the rule and its rationale are inapplicable. This Court is not required to follow the opinion of the Attorney General. Traverse City School Dist v Attorney General, 384 Mich 390, 410 fn 2; 185 NW2d 9, 17 (1971). Garcia v City of Warren Civil Service Comm, 78 Mich App 603, 608; 261 NW2d 19, 22 (1977), David Walcott Kendall Memorial School v Grand Rapids, 11 Mich App 231, 237; 160 NW2d 778, 781 (1968). Instead, we accept the opinion of the Attorney General as expressing one of two possible, reasonable interpretations, but do not view the reasoning of the opinion as compelling.
Defendant also contends that the subsequent amendment of the statute to conform to the Attorney General’s interpretation of the old statute reflects a legislative intention to clarify the ambiguity by making explicit the Legislature’s prior intent. The difficulty with this argument is that we cannot know whether the change was intended by the Legislature to be one of form or substance. Generally, an amendment is to be construed, unless a different intent is manifest, as changing the meaning of the statute. Bonifas-Gorman Lumber Co v Unemployment Compensation Comm, 313 Mich 363, 369; 21 NW2d 163, 165 (1946). Thus, one inference which may be drawn from the amendment is that the Legislature viewed the prior statute as having the meaning advanced by plain*775tiff, and changed the meaning to that advanced by defendant. On the other hand,
" '[i]f the amendment was enacted soon after controversies arose as to the interpretation of the original act, it is logical to regard the amendment as a legislative interpretation of the original act — a formal change— rebutting the presumption of substantial change.’ ” Detroit Edison Co v Dep’t of Revenue, 320 Mich 506, 520; 31 NW2d 809, 816 (1948), quoting 1 Sutherland, Statutory Construction (3d ed), § 1931, p 418, see Detroit Edison Co v Janosz, 350 Mich 606, 613-614; 87 NW2d 126, 130 (1957).
Thus, we may also infer that the Attorney General’s opinion was in response to a controversy concerning the correct interpretation of the statute, and the Legislature reacted thereto by making clear its prior intent.
Whatever might have been the understanding of the Legislature as to the prior meaning of the statute, that understanding would only be evidence to aid in our interpretation, and not disposi-tive.
"The controlling test as to the meaning of a statutory provision is always the legislative intent when fairly ascertainable. But the 'intent’ referred to is the one entertained by the legislature at the time of the passage of the act, and not the intent expressed by a subsequent amendment. In the instant case, to interpret the subsequent amendment as an indication of the legislature’s original intent would be mere speculation, not judicial construction.” Iron Street Corp v Unemployment Compensation Comm, 305 Mich 643, 655; 9 NW2d 874, 879 (1943), Detroit Edison Co v Dep’t of Revenue, supra, at 519; 31 NW2d at 815.
The primary rule of statutory construction,
*776"is to ascertain and give effect to the intention of the legislature. All [other rules] serve but as guides to assist the courts in determining such intent with greater degree of certainty”. Grand Rapids v Crocker, 219 Mich 178, 182; 189 NW 221, 222 (1922).
Having determined that extrinsic aids to interpretation do not provide a dispositive answer to the instant issue, we turn to the words of the statute itself.
The intention of the Legislature is manifest. The purpose of the statute is to provide retirement credit for that time during which members of the retirement system were unable to continue their school employment because of a conflicting obligation to serve their country in the armed forces. Ordinarily that obligation would conflict with a teaching career at the time of draft or enlistment, and we may infer that the Legislature assumed without expressly considering that draft or enlistment would automatically lead immediately to active duty. We decline to write into the statute a distinction not then made by the Legislature, which would be essentially arbitrary and thwart the general purpose of the statute in cases such as this. Upon plaintiffs enlistment, he was obligated to serve his country in a capacity which interrupted his teaching career. His sacrifice was no less than it would have been had he first been placed on active duty and then sent to school. We are certain that, had the Legislature expressly considered this type of situation, it would have drawn the statute in such a manner as to make clear its intention to allow the credit.
Reversed. No costs, public question.
M. B. Breighner, J., concurred.