Hi as far as I know, having checked this out myself it's just the time that's affected. Say you worked 10 yrs full time followed by 20yrs half time (job sharing for example) and then your final 10 yrs full time you would be credited with 30 yes employment.
When calculating your pension the calculation is based on your finishing salary and years of service. Whether you're part time or full time your pension us calculated on the full rate of pay for your grade but where you lose out is on the years service.
Example; 40yrs full service with a final salary of say €60k, lump sum is calculated by years x salary x (3/80) so this would be €90000. For an employee that had taken leave as described above it would be €67,500. The annual pension is calculated slightly different as they take jnto account the state pension but I think (and I'm open to correction) that it's slightly less than one third of the lump sum per annum.
You have the option yo increase your lump sum payment with AVC's to account for the loss but are subject to 1.5 times final salary amount I think.
Hope this explains it