Augmenting an old date

Two columns in my PostgreSQL db are type 'date' (formatted 'YYYY-mm-dd'): 'start_date' and 'expiry_date'. What I cannot seem to figure out is how to augment the 'expiry_date' either by 30 days, 60 days, or 1 year. I've tried the date function in PHP (getdate) but the problem is that it appears to need a timestamp of "today". The dates that I'm trying to augment are sometimes a year or two ago. This doesn't work: $new_expiry_date = $expiry_date("Y-m-d", mktime(0,0,0, date(Y), date(m), date(d) + 60))); I assume it's because the '$expiry_date' should be simply 'date', but that would give the current date which is not what is wanted. Is there anyway to set 'date' as '$expiry_date'? Suggestions, admonitions, and general advice will be greatly appreciated. Btw, I've searched the archives, and haven't found anything quite on this topic. Tia, Andre -- Please pray the Holy Rosary to end the holocaust of abortion. Remember in your prayers the Holy Souls in Purgatory. May God bless you abundantly in His love! For a free Cenacle Scriptural Rosary Booklet: http://www.webhart.net/csrb/