如何获取特定时间的UTC时间戳？

import datetime

# 获取当前时间的UTC时间戳
utc_timestamp = datetime.datetime.utcnow().timestamp()

# 获取特定时间的UTC时间戳
specific_time = datetime.datetime(2022, 1, 1, 0, 0, 0)
specific_utc_timestamp = specific_time.timestamp()

// 获取当前时间的UTC时间戳
var utcTimestamp = new Date().getTime();

// 获取特定时间的UTC时间戳
var specificTime = new Date("2022-01-01T00:00:00Z");
var specificUtcTimestamp = specificTime.getTime();

import java.util.Date;
import java.time.Instant;

// 获取当前时间的UTC时间戳
long utcTimestamp = Instant.now().getEpochSecond();

// 获取特定时间的UTC时间戳
Date specificTime = new Date(2022 - 1900, 0, 1, 0, 0, 0);
long specificUtcTimestamp = specificTime.toInstant().getEpochSecond();