Timing way off..help.

My car was running mint...sat few days and is missing// not revving up good almost like only half firein...all plugs getting spark but with inline tester on light is not consant when Rev..can still see it blink/ coil getting good spark.. pick-up is good and correct gap. ..but I'm checking the timing and it's like few inches from where mark is...how could it get so far off and can you even adjust distributor that much??.. or maybe something eles happened to it..any help.sorry if seems dumb..I'm lost .. checked all I could think of..any suggestions would help...I'm lost now...lol