import numpy as np

def fix_timestamps(tstmp, offsets=None):
    tstmp = tstmp.astype(np.int64)
    rollover, = np.where(np.diff(tstmp) < 0)
    if offsets is None:
        offsets = tstmp[rollover]
    for j, i in enumerate(rollover):
        tstmp[(i + 1):] = tstmp[(i + 1):] + offsets[j]
        # offsets[j:] += tstmp[i]
    cum_offsets = np.cumsum(offsets)
    return tstmp, offsets, cum_offsets