get min diff between time

import re
import sys

MAX_INT = sys.maxsize

def get_time_from_string(time_string):
    time_value = "".join(re.split("[a-zA-Z]", time_string))
    time_format = "".join(re.split('\d+:\d+', time_string)).lower()
    [hours, minutes] = time_value.split(":")
    hours = int(hours) if int(hours) < 12 else 0
    minutes = int(minutes)
    time_in_minutes = hours * 60 + minutes
    if time_format == 'pm' and hours < 12:
        time_in_minutes += 720  # 12hours in min

    return time_in_minutes

def get_min_diff(arr):
    times_in_minutes = [get_time_from_string(i) for i in arr]
    times_in_minutes.sort(reverse=True)
    min_diff = MAX_INT
    i = 0
    while i<len(times_in_minutes)-1:
        diff = times_in_minutes[i] - times_in_minutes[i+1]
        if diff < min_diff:
            min_diff = diff
        i += 1
    print(min_diff)
    return min_diff

get_min_diff(["10:00am", "11:45pm", "5:00am", "12:01am"])