Normally one considers 365 days in a year or 365xx24=8760 hours in a year
and hence in 34.5 years we have 34.5xx8760=302220 hours.
However, it is well known that there are about 6 hours more every year, due to which one full day is added every four years in the leap year but again every 100^(th) year is not a leap year as in fact a year has somewhat less than 365 days and 6 hours.
In fact the year has 5.81277 hours more than 8760 hours stated above i.e, 8765.81277 hours
Hence, in 34.5 years we have 34.5xx8765.81277=302420.54 hours approximately.
