graphs.py 文件源码

def monthdelta(date, delta):
    m = (date.month + delta) % 12
    y = date.year + (date.month + delta - 1) // 12
    if not m:
        m = 12
    d = min(date.day, [31, 29 if y % 4 == 0 and not y % 400 == 0
                       else 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
                       ][m - 1])
    return date.replace(day=d, month=m, year=y)