检查日期是否在世界某处有效

Question

如何检查给定的时间戳是否仍然存在于全球某处？

例如，假设我的时间戳类似于 2017 年 5 月 10 日下午 3:49。今天世界上有没有哪个地方是 2017 年 5 月 10 日下午 3:49？

Answer 1

检查时间戳是否在 UTC+14 和 UTC-12 之间。

from datetime import datetime, timedelta

def is_a_today_somewhere(timestamp):
  now = datetime.now()
  latest = now + timedelta(hours=-12)
  earliest = now + timedelta(hours=14)
  return  latest <= datetime.fromtimestamp(timestamp) <= earliest

now = datetime.now()                        # now
timestamp = datetime.timestamp(now)
print(is_a_today_somewhere(timestamp))      # prints True

now = datetime.now() + timedelta(hours=7)   # +7 hours from now
timestamp = datetime.timestamp(now)
print(is_a_today_somewhere(timestamp))      # prints True

now = datetime.now() + timedelta(hours=-23) # -23 hours from now
timestamp = datetime.timestamp(now)
print(is_a_today_somewhere(timestamp))      # prints False

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注意，检查之间应该是一个包容性。但是由于从生成时间戳到检查其有效性所花费的时间，时间戳几乎不在最新时区的边缘情况可能会出现错误。

from datetime import datetime, timedelta

def is_a_today_somewhere(timestamp):
  now = datetime.now()
  latest = now + timedelta(hours=-12)
  earliest = now + timedelta(hours=14)
  return  latest <= datetime.fromtimestamp(timestamp) <= earliest

now = datetime.now() + timedelta(hours=-12)  # -12 hours from now; barely in today 
timestamp = datetime.timestamp(now)
print(is_a_today_somewhere(timestamp))      # May print False

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Answer 2

使用与 UTC 的标准偏差，即最大值 +14 和最小值 -12，您可以比较时间戳并查看时间戳是否介于最大值和最小值之间。

from datetime import datetime


def is_valid_time(search_timestamp):
    utc_timestamp = datetime.timestamp(datetime.utcnow())
    max_timestamp = utc_timestamp + (14*60*60)  # max time is utc+14
    min_timestamp = utc_timestamp - (12*60*60)  # min time is utc-12

    # check if time in range
    if min_timestamp <= search_timestamp <= max_timestamp:
        return True
    return False

# Test cases
now = datetime.timestamp(datetime.now())
# false
print(is_valid_time(3))

# false
print(is_valid_time(now + (16*60*60)))

# true
print(is_valid_time(now))

Answer 3

您可以通过将所有时区的当前时间与提供的时间进行比较来进行检查。

这里有一个函数可以为你做到这一点：

import datetime
deviations_from_utc = (-12, -11, -10, -9.5, -9, -8, -7, -6, -5,
                   -4, -3.5, -3, -2, -1, 0, 1, 2, 3, 3.5, 4, 4.5, 5,
                   5.5, 5.75, 6, 6.5, 7, 8, 8.5, 8.75, 9, 9.5, 10, 
                   10.5, 11, 12 , 12.75, 13, 14)
def is_current(t):
    n = datetime.datetime.utcnow()
    provided_time = (t.year, t.month, t.day, t.hour, t.minute)
    for time in deviations_from_utc:
        at = n + datetime.timedelta(hours=time)
        at_time = (at.year, at.month, at.day, at.hour, at.minute)
        if provided_time == at_time:
            return True
    return False

deviations_from_utc 包含所有使用的与 utc 时间的偏差。该列表取自 this 维基百科文章。