varying pay periods

SUGGESTED

Our normal pay period is bimonthly (24 pay days)

One person's payroll does not make sense because some periods, his pay stub is correct (march1-15, then 16-30) but some months, the pay stub is incorrect (april1-15, then 25-31).

The bi-monthly salary based on yearly wage is correct for all pay stubs. 

I am not sure if this was done by the person before me in payroll. 

I am wondering if this could have changed the tax amounts at all? CPP / EI / Income tax

Am I able to edit the dates on the paystub for this person without it have consequences for year end T4 or any further confusion? 

He is under the impression that somehow he has paid more in taxes because of this. 

Please help me solve this problem.