This appellant pleaded not guilty to being an unauthorized absentee from the Naval Support Activity, Philadelphia, from 25 February 1974 until 12 February 1976.
A general court-martial with members found him guilty of unauthorized absence from the Support Activity during the period from 25 August 1974 until 12 February 1976 — in effect reducing the period of absence by adding 6 months to the commencement date alleged in the specification. The sentence awarded and previously approved consists of a bad conduct discharge and confinement for 1 month.
Official documents — -service record entries — proffered to the court as prosecution evidence showed commencement and termination of the absence as alleged in the specification before the court.
Appellant in testimony to the court stated he sought an undesirable discharge resultant from contemplated disciplinary action for a previous unauthorized absence. He further maintained he was advised he was granted leave and was sent home to await that discharge, subject to recall if it was decided to take disciplinary action against him. He went home. He did not hear again from the Navy until late November 1974 when his father received a letter concerning disposition of his personal effects stored from the previous absence. The letter noted that due to the nature of discharge the appellant was not entitled to receive his uniforms. About 13 months later appellant received orders from the Chief of Naval Personnel advising him that records showed he was a deserter since 25 February 1974. Appellant began inquiries as to his military status and ultimately surrendered to authorities on 12 February 1976.
The remainder of the evidence of record is essentially negative in character — e. g., no effort by appellant to inquire as to his status until December 1974 and no showing some required reports were made on the absence alleged. Nowhere does the date 25 August 1974 appear in the record, prior to findings of guilt.
*692In his instructions to the court members the trial judge advised that:
. as long as the accused operated under an honest and reasonable mistake of fact, he is not guilty of being absent without proper authority. Should you find, beyond a reasonable doubt, that at some time later than 25 February 1974, the accused was disabused of such mistaken belief and no longer honestly and reasonably believed himself an authorized absentee, then you may find the accused guilty of an unauthorized absence commencing at a time which you have no reasonable doubt that the accused was absence [sic] without proper authority. (R. 95).
The court members’ reasons for their findings remain a secret. It is clear that appellant’s guilt of an unauthorized absence commencing on 25 February 1974 was not accepted by the members, for he was acquitted of that offense. Thus, the issue to be resolved is whether appellant may be convicted of the absence offense found by the court, whereby the commencement date of the absence was changed to a later date as permitted by the military judge’s instructions on findings.
The puzzlement of the trial judge as to the substance of the offense of unauthorized absence is appreciated. That an unauthorized absence is committed the instant the absence commences and that it is not a continuing offense seems clear. United States v. Lovell, 7 U.S.C.M.A. 445, 22 C.M.R. 235 (1956); United States v. Harris, 21 U.S.C.M.A. 590, 45 C.M.R. 364 (1972). Further, it is clearly implicit in recent decisions by the United States Court of Military Appeals that the commencement date of an unauthorized absence may be lawfully changed to a later date than that alleged. United States v. Harris, supra; United States v. Davis, 22 U.S.C.M.A. 241, 46 C.M.R. 241 (1973).
How then may an “instantaneous” offense occur later during the absence than alleged, without substantially changing the offense? It must be concluded that it does only because of the peculiar nature of the unauthorized absence offense itself. The offense requires a commencement date, lack of authority to be absent and a return date. The latter date is necessary to show the severity of the offense and to determine the maximum punishment. Each of these elements is amalgamated into the whole offense of unauthorized absence. The commencement date of the absence may vary dependent on the facts and circumstances in each case, for it is but one offense. Although the offense is not a continuing offense, the circumstances involved in a given case may show the absence commenced at a date later than that alleged and still be a part of the same offense. Such is the construction of the law of unauthorized absence, as amplified by case law, considered applicable to this case. See Winthrop, Military Law and Precedents, 255 (2d ed. rev. 1920), and citations, supra.
The foregoing principles may be melded into a rule of law just as the military judge did in his instruction to the court. No error is apparent in the instruction when taken in the abstract sense, based on case law and logic. The instruction and the law leave the court free to choose any date within a 717-day time span as the commencement date of the single absence, if it is convinced of that date beyond reasonable doubt. It appears that is exactly the occurrence which took place at this trial. Since the instruction was correct the application of that law to the case must be examined.
The problem in the case lies in the evidentiary proof available for use in determining guilt. Examination of the record fails to show what, if any, evidence led the court to conclude the absence commenced on 25 August 1974. No citation of evidence establishing that date is found in the briefs before this court — the Government seemingly contends the court concluded the appellant’s mistake of fact was neither honest nor reasonable at the end of 6 months. No explanation is evident as to the reason a 6-month period of time is more appropriate to allow the appellant to recognize his mistake than any other time span over the *693two-year period in issue. The evidence does not establish the commencement date of the absence beyond reasonable doubt — particularly when the appellant’s belief that he was being discharged was buttressed by a letter from the Navy in November 1974, 9 months after he left the Navy. Mere speculation appears as the basis for ascertaining the commencement date of the unauthorized absence later than alleged. Speculation may not be the reason for criminal conviction. Proof is required.
The foregoing failure of proof requires the findings be disallowed. Such action obviates the need to address the remaining assignments of error set out by the appellant. However, in passing, the appellant’s attack on the validity of the oath to the charge is specifically rejected. United States v. Johnson, 3 M.J. 623 (N.C.M.R.1977). The statute of limitations had not run. The first assignment of error is without merit.
The findings and sentence are set aside and the charge is dismissed.
Judge GLADIS concurs.