How to make a command that will show all the hours and minutes for being in the voice on the server?

Question

Python

How to make a command that could show all the hours and minutes of being on the server in voice channels when it is entered? The command itself is already there and @bot.event:

@bot.event
async def on_voice_state_update(member, before, after):
    with open('c:/Python/TOXBOT/database.json', 'r', encoding = "utf-8") as file:
        data = json.load(file)
    author = member.id
    if before.channel is None and after.channel is not None:
        t1 = time.time()
        data[str(author)]['Онлайн'] = t1
    elif before.channel is not None and after.channel is None and author in tdict:
        t2 = time.time() 
        print(t2-tdict[author])
        data[str(author)]['Онлайн'] + data[str(author)]
    with open('c:/Python/TOXBOT/database.json', 'w', encoding = "utf-8") as file:
        json.dump(data, file)

What is missing and what errors (if any)? discord.py