Is it really part time if you work 7hours per day, 6 days per week.
You could (7hours/day) * (6 days/week) * (52 weeks / year) * (2 years) / (37.5 hours/week* 52 weeks/year)
Just confirm that full time work experience is 37.5 hours / day.
Since you worked around 42 hours per week, you could go the easier route and just say you worked 2 years full time.
What do others think?