require 'date' # this is just to get the ABBR_MONTHNAMES list

input = "[22/May/2011:23:02:21 +0000]"
# this regex captures the numbers and month name
pattern = %r{^\[(\d{2})/(\w+)/(\d{4}):(\d{2}):(\d{2}):(\d{2}) ([+-]\d{4})\]$}
match = input.match(pattern)
# MatchData can be splatted, which is very convenient
_, date, month_name, year, hour, minute, second, tz_offset = *match
# ABBR_MONTHNAMES contains "Jan", "Feb", etc.
month = Date::ABBR_MONTHNAMES.index(month_name)
# we need to insert a colon in the tz offset, because Time.new expects it
tz = tz_offset[0,3] + ':' + tz_offset[3,5]
# this is your time object, put it into Mongo and it will be saved as a Date
Time.new(year.to_i, month, date.to_i, hour.to_i, minute.to_i, second.to_i, tz)

一些注意事项:

• 我假设月份名称与ABBR_MONTHNAMES列表中的名称相同，否则，只需创建您自己的列表即可.
• 从不使用Date.parse来解析日期，这太慢了，对于使用相同实现的DateTime.parse，Time.parse也是如此.
• 如果您解析许多不同的日期格式，请查看 home_run gem.
• 如果您做很多这样的事情(就像您在解析日志文件时经常做的那样)，请考虑不使用正则表达式.使用String#index，#[]和#split提取所需的零件.

• I assumed that the month names are the same as in the ABBR_MONTHNAMES list, otherwise, just make your own list.
• Never ever use Date.parse to parse dates it is incredibly slow, the same goes for DateTime.parse, Time.parse, which use the same implementation.
• If you parse a lot of different date formats check out the home_run gem.
• If you do a lot of these (like you often do when parsing log files), consider not using a regex. Use String#index, #[] and #split to extract the parts you need.

如果您想尽快执行此操作，则以下内容可能更合适.它不使用正则表达式(有用，但速度不快):

If you want to do this as fast as possible, something like the following is probably more appropriate. It doesn't use regexes (which are useful, but not fast):

date = input[1, 2].to_i
month_name = input[4, 3]
month = Date::ABBR_MONTHNAMES.index(month_name)
year = input[8, 4].to_i
hour = input[13, 2].to_i
minute = input[16, 2].to_i
second = input[19, 2].to_i
tz_offset = input[22, 3].to_i * 60 * 60 + input[25, 2].to_i * 60
Time.new(year, month, date, hour, minute, second, tz_offset)

它利用了所有字段都具有固定宽度的事实(至少我认为它们确实有宽度).因此，您所需要做的就是提取子字符串.它还将时区偏移量计算为数字而不是字符串.

It takes advantage of the fact that all fields have fixed width (at least I assume they do). So all you need to do is extract the substrings. It also calculates the timezone offset as a number instead of a string.