Editing 1467: Email

{{comic
| number    = 1467
| date      = December 31, 2014
| title     = Email
| image     = email.png
| titletext = My New Year's resolution for 2014-54-12/30/14 Dec:12:1420001642 is to learn these stupid time formatting strings.
}}

==Explanation==
Despite being in popular use since 1998 when free email providers appeared and having existed since before 1982 when {{w|SMTP}} was established, [[Beret Guy]] apparently doesn't understand what {{w|email}} is, even though he maintains a web page that includes his email address. [[Megan]] wonders how else he expects electronic messages to be sent. She explains that one must check email regularly, making a slight at {{w|voicemail}}, which she implies is not worth ever checking.

Beret Guy offers two alternatives: {{w|Fax}} and {{w|Snapchat}}. Megan refers to Snapchat as "the naked pic thing", calling to mind how many of its users send naked pictures of themselves over the Internet. Beret Guy replies that people use fax machines for more than just "faxting" (a made-up term similar to {{w|sexting}}), implying not only that many people send sexual content via fax, but also that he associates fax machines with such acts rather than Snapchat, despite faxing being a technology that predates SMTP by more than a century. Beret Guy knows what a fax is, which implies he is very behind in the technology world, so it makes sense he doesn't know what email is. But he also knows what Snapchat is, which was very popular around the time of this comic. Either Beret Guy heard about it in a similar way to email, or he definitely knows what it is and/or uses it. What's strange is that if Beret Guy knows what Snapchat is, he should know what email is as well, since you need to provide an email account in order to create a snapchat account.

The title text, which could be [[Randall]]'s New Year's resolution for 2015, refers to various date/time formats. In programming, a point in time (e.g. the current system time) is usually stored and processed as a single number that represents the count of seconds that have elapsed since a given starting time known as "epoch" (the Unix standard epoch is January 1, 1970 at midnight, {{w|UTC}}). In order to make sense to people, this number must be converted to a human-readable format, but programmers must choose a format that best meets the needs of their users. This can be a complicated problem to solve, given that there are many different standard formats for different regions, different levels of precision for different applications, and differences between "universal time" and a user's local time zone. Randall has previously advocated for widespread adoption of the {{w|ISO 8601}} format as a universal standard.

The title text also probably references a twitter outage that took place on December 29, which was blamed on an [http://www.theguardian.com/technology/2014/dec/29/twitter-2015-date-bug error in a date format string].

Most programming languages provide functions to create a custom date-format string using "tokens" that represent different parts of the date/time. Here, Randall appears to have used one of these functions with the string "%Y-%M-%D %h:%m:%s", which looks like it should produce a date and time as "Year-Month-Day Hour:Minute:Second". However, he used the wrong tokens for this:

*%Y = 4-digit year (2014)
*%M = minute (54)
*%D expands to %m/%d/%y, which is "month/day/2-digit year" in the user's local time zone rather than UTC. ("12/30/14" - see below)
*%h = abbreviated month name ("Dec")
*%m = 2-digit month (12)
*%s = Unix timestamp (1420001642 seconds since epoch)

The "%s" token shows us the actual {{w|Unix time|Unix timestamp}} used (1420001642), which corresponds to 2014-12-31 at 04:54:02 UTC. The format string shown above thus yields "2014-54-12/30/14 Dec:12:1420001642". Note that the middle portion of this string shows "12/30" instead of "12/31" - this is due to the %D token expressing the date in Randall's local time zone (Eastern Standard Time, or EST), which is 5 hours before UTC. The time there was 23:54:02, or just before midnight, on the previous day.

The correct format string for Randall's apparent desired result is "%Y-%m-%d %H:%M:%S", which gives the string "2014-12-31 04:54:02" (UTC) or "2014-12-30 23:54:02" (EST). Given the similarity between Randall's string and the correct one, it is easy to see how this type of formatting is confusing and often frustrating for programmers - particularly those not intimately familiar with these functions.

Randall previously addressed date/time formatting in [[1179: ISO 8601]] and [[1340: Unique Date]] (the latter of which uses a formatting string correctly).

This was the second comic in a row with Megan holding a smart phone, the first being [[1466: Phone Checking]]. The comic before that one was also about smart phones: [[1465: xkcd Phone 2]].

==Transcript==
:[Megan approaches Beret Guy.]
:Megan: Any New Year's resolutions?
:Beret Guy: Gonna figure out what email is.
:Megan: ''...Email?''

:[Megan points to her phone.]
:Beret Guy: People always say they're sending them. They sound really into it, so I always nod, but I have no idea what it is.
:Megan: You have an address on your website!

:[Megan and Beret Guy walking.]
:Beret Guy: Oh, ''that's'' what that thing is.
:Megan: Email is important! You can't just ''never'' check it. It's not like voicemail.

:Beret Guy: Can't they just send messages ''normally?''
:Megan: How?
:Beret Guy: Fax! Or Snapchat.
:Megan: ...The naked pic thing?
:Beret Guy: Fax machines aren't ''just'' for faxting!

==Trivia==
The Unix timestamp is a standard method of keeping time by counting the absolute number of seconds that have elapsed since a set point in time known as "epoch", defined as midnight on January 1, 1970, Coordinated Universal Time (UTC). Epoch, in {{w|ISO-8601}} format, is "1970-01-01T00:00:00Z", where Z indicates UTC.

The timestamp in this comic's title text (1420001642) is 1,420,001,642 seconds since epoch. The process of converting that number into a human-readable time is as follows:

*Years since 1970 = 1,420,001,642 seconds / 60 seconds per minute / 60 minutes per hour / 24 hours per day / 365.25 days per year
**This yields 44 years plus 31,467,242 seconds.
**The year for the timestamp is 1970 + 44 years = '''2014'''.
***Note: The year calculation specifies 365.25 days per year to account for {{w|leap year|leap years}} (every fourth year adds an extra day).  Also note that 2014 is not a leap year.
*Days since start of year = 31,467,242 seconds / 60 seconds per minute / 60 minutes per hour / 24 hours per day
**This yields 364 days plus 17,642 seconds.  Given January 1 is considered the ''first'' day of the year, this means we are on the 365th day of 2014.
**The 365th day of a non-leap year is '''December 31'''. December is the '''12th month''' in the Gregorian calendar.
*The remaining seconds can be converted into a time:
**Hours since start of day = 17,642 seconds / 60 seconds per minute / 60 minutes per hour = '''4 hours''' plus 3,242 seconds
**Minutes since start of hour = 3,242 seconds / 60 seconds per minute = '''54 minutes''' plus '''2 seconds'''

Thus, Randall's timestamp represents the time "'''2014-12-31'''T'''04:54:02'''Z" (again in ISO-8601 format).

{{comic discussion}}
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