如何将DateTime转换为自1970年以来的秒数？

DateTime dateTime = DateTime.Now;
DateTime epoch = new DateTime(1970, 1, 1);
TimeSpan timeSpan = dateTime - epoch;
long seconds = (long)timeSpan.TotalSeconds;

import java.time.Instant;

Instant now = Instant.now();
long seconds = now.getEpochSecond();

import datetime
import time

now = datetime.datetime.now()
epoch = datetime.datetime(1970, 1, 1)
time_span = now - epoch
seconds = int(time_span.total_seconds())

const now = new Date();
const epoch = new Date(1970, 0, 1);
const timeSpan = now - epoch;
const seconds = Math.floor(timeSpan / 1000);