1514: PermaCal

2015-04-20T13:16:53Z

J16sdiz: /* Explanation */

{{comic
| number = 1514
| date = April 20, 2015
| title = PermaCal
| image = permacal.png
| titletext = The flood of PermaCalNTP leap-second notifications was bad enough, but when people started asking for millisecond resolution, the resulting DDOS brought down the internet.
}}

==Explanation==
This comic proposes a new calendar system. This is similar to comic [[1061: EST]]. In this new calendar system, the date stays constant, and only changes with {{w|February 29|leap days}}. PermaCal is a portmanteau of the words "permanent" and "calendar".

In the comic, the date is the same as the day before the comic was released, the 19th of April, 2015.

Leap days in the {{w|Gregorian calendar}} are days added to the end of {{w|February}} every year that is a multiple of 4, but not by 100, unless it's also a multiple of 400. The purpose is to sync the calendar with Earth's orbit without having a partial day each year.

NTP servers are used to keep local computer time from drifting. {{w|Leap second|Leap seconds}} normally account for the differences in the length of our 24 hour day and a solar day (the time taken for Earth to rotate so the same point points towards the sun), and are announced several months before hand, but in the context of this comic probably refer to a system with constant time, and the time is adjusted by an NTP call every second. The title text refers to the bandwidth used by correcting the time in every millisecond resolution (maybe 100ms every few months like [http://www.quadibloc.com/science/cal06.htm] and [http://fixunix.com/ntp/68074-leap-millisecond.html]), resulting in a {{w|DDoS}}, and is probably a reference to other retail consumer products that have {{w|Denial-of-service_attack#Unintentional_denial-of-service|unintentionally}} caused DDoS attacks because of a flaw in implementation. See here an example of a real-life unintentional [http://comments.gmane.org/gmane.org.operators.swinog/10055 DDOS attack].

==Transcript==
:[Megan and Cueball are in the panel. Cueball appears to be holding a phone, tapping.]
:Megan: What day is it?
:Cueball: Sunday the 19th.
:Megan: But you said it was the 19th yesterday.
:Cueball: It changed ''again''? Crap, better add another leap day.
:[Caption below the panel:]
:My simplified calendar system assumes the date never changes, then corrects any drift via leap days.

==Trivia==
*The "H" in Megan's version of "19TH" is missing the upper part of the left bar, making it look like an mirrored "h". This must be unintended, since the H in "19TH" is written correctly when Cueball says it. Also only capital letters are used in the comics (except in special cases).

{{comic discussion}}


[[Category:Comics featuring Cueball‏]]
[[Category:Comics featuring Megan‏]]
[[Category:Time management]]
[[Category:Portmanteau]]

1514: PermaCal

2015-04-20T13:15:52Z

J16sdiz: /* Explanation */

{{comic
| number = 1514
| date = April 20, 2015
| title = PermaCal
| image = permacal.png
| titletext = The flood of PermaCalNTP leap-second notifications was bad enough, but when people started asking for millisecond resolution, the resulting DDOS brought down the internet.
}}

==Explanation==
This comic proposes a new calendar system. This is similar to comic [[1061: EST]]. In this new calendar system, the date stays constant, and only changes with {{w|February 29|leap days}}. PermaCal is a portmanteau of the words "permanent" and "calendar".

In the comic, the date is the same as the day before the comic was released, the 19th of April, 2015.

Leap days in the {{w|Gregorian calendar}} are days added to the end of {{w|February}} every year that is a multiple of 4, but not by 100, unless it's also a multiple of 400. The purpose is to sync the calendar with Earth's orbit without having a partial day each year.

NTP servers are used to keep local computer time from drifting. {{w|Leap second|Leap seconds}} normally account for the differences in the length of our 24 hour day and a solar day (the time taken for Earth to rotate so the same point points towards the sun), and are announced several months before hand, but in the context of this comic probably refer to a system with constant time, and the time is adjusted by an NTP call every second. The title text refers to the bandwidth used by correcting the time in every millisecond resolution [http://fixunix.com/ntp/68074-leap-millisecond.html], resulting in a {{w|DDoS}}, and is probably a reference to other retail consumer products that have {{w|Denial-of-service_attack#Unintentional_denial-of-service|unintentionally}} caused DDoS attacks because of a flaw in implementation. See here an example of a real-life unintentional [http://comments.gmane.org/gmane.org.operators.swinog/10055 DDOS attack].

==Transcript==
:[Megan and Cueball are in the panel. Cueball appears to be holding a phone, tapping.]
:Megan: What day is it?
:Cueball: Sunday the 19th.
:Megan: But you said it was the 19th yesterday.
:Cueball: It changed ''again''? Crap, better add another leap day.
:[Caption below the panel:]
:My simplified calendar system assumes the date never changes, then corrects any drift via leap days.

==Trivia==
*The "H" in Megan's version of "19TH" is missing the upper part of the left bar, making it look like an mirrored "h". This must be unintended, since the H in "19TH" is written correctly when Cueball says it. Also only capital letters are used in the comics (except in special cases).

{{comic discussion}}


[[Category:Comics featuring Cueball‏]]
[[Category:Comics featuring Megan‏]]
[[Category:Time management]]
[[Category:Portmanteau]]

explain xkcd - User contributions [en]

1514: PermaCal

1514: PermaCal