Time Required for OP manga

Average amount of time it takes to read a manga page = 10-15 minutes (assuming you’re not a slowpoke)

Average = 10+15)/2 = 12.5 Minutes (One Piece is an action shonen so most pages will be quicker than this)

Average manga chapters are 20-30 pages (Average of those is 25)

25 * 12.5 = 312.5 Minutes for one chapter

OP manga ≈ 900 chapters so

900 * 313.5 Minutes = 282150 minutes

282150/60 = 4702.5 hours

4702.5/24 = 195.9375 Days

Average month ≈ 30 days

195.9375/30 = 6.53125 Months