pyTimePlusDuration

def get_time(prompt, maxhr):
    while True:
        sin = input("\n" + prompt)
        sinsplit = sin.split(':')
        if len(sinsplit) != 2:
            print("Invalid")
            continue
        if not (sinsplit[0] + sinsplit[1]).isdecimal():
            print("Invalid")
            continue
        h = int(sinsplit[0])
        m = int(sinsplit[1])
        if h > maxhr or m > 59:
            print("Invalid")
            continue
        break
    return h, m


while True:
    hh, mm = get_time("Enter start time as hh:mm in 12-hour clock format: ", 12)
    while True:
        ap = input("Enter 'am' or 'pm': ").lower()
        if ap in ["am", "pm"]:
            break
        print("Invalid")
    if hh == 0 and ap == "pm":
        print("Invalid")
        continue
    break

# Convert start time to 24-hour format

if ap == "pm" and hh < 12:
    hh += 12
if ap == "am" and hh == 12:
    hh = 0

print(f"Start time is: {hh:02d}:{mm:02d}")

dh, dm = get_time("Enter duration as hh:mm (max 24 hours): ", 23)
mm += dm
hplus, mm = divmod(mm, 60)
hh += dh
hh += hplus

ap = "am"
hh = hh % 24
if hh > 11:
    ap = "pm"
if hh > 12:
    hh -= 12
if hh == 0:
    hh = 12

print(f"Finish time is {hh:02d}:{mm:02d} {ap}")