Periods of absence of not more than ninety days in any one calendar year shall not be considered as breaking continuity of service. Periods of absence of more than ninety days by reason of a leave of absence granted by the appropriate authority of the municipality or where the absence is occasioned by disability necessitating the regular attendance of a physician, unless such attendance is declared unnecessary by medical authority satisfactory to the Retirement Commission, or by reason of layoff, shall not be considered as breaking continuity of service, but such periods shall not be included in determining the amount of the retirement allowance. Any member who entered any branch of the armed forces of the United States between September 16, 1940, and July 26, 1945, or who enters any of said services while the United States is at war, or engaged in any hostilities or during times of national emergency, whether declared or undeclared, or any acts incident thereto, and who is reemployed by the municipality within six months following the termination of such service, unless this period is further extended by reason of disability incurred in the course of such service, shall be credited with the period of such service to the same extent as though he had been continuously employed by the municipality and shall be considered to have made the contributions required by this part based on his regular rate of pay at the time of the commencement of such service. The period of service of any member as a full-time employee of any municipality merged or consolidated either before or after the acceptance of this part with a participating municipality shall be counted for the purpose of qualifying such member for retirement and for the purpose of computing the amount of his retirement allowance, provided such combined services shall have been continuous as defined above.