Calendars and dates

Why the codex has calendars 
 Some facts are only true for a while. A captain holds a rank until she's promoted; a city stands until it falls; a character is twelve in one book and forty in the next. To say when a fact applies, the codex needs a way to write dates—and your world may not count years the way ours does. So each universe has at least one calendar, and a fact can say "from here, to there" on it. 
 If your books are set in the ordinary world, you can leave all of this alone. Every universe starts with a Gregorian calendar, and that's the one you'll be offered. 
 Where it lives 
 In the codex, click Setup at the top right. The rail that opens has a Calendar system card. The default calendar is already there, named Gregorian ; rename it if your story calls it something else, and there's a table beneath, How other worlds would write theirs , showing how a Star Wars, Star Trek, Tolkien, Dune or Westeros calendar would be set up, in case you'd like to borrow one. 
 
 Screenshot: the codex's Setup rail with the Calendar system card open, showing the default calendar named Gregorian and, beneath it, the table How other worlds would write theirs. 
 What a calendar needs 
 Calendar name —what you see. Gregorian , Stellar date , Imperial reckoning . 
 Dates are written as —how you'll type a date for this calendar. Five ways: 
 
 a year, with an era if any : 2024 · 68 CE · 44 BC · 4 ABY. The usual choice. 
 month.day.year : 11.04.8927. (Aeon 14's stellar dates are written this way.) 
 day.month.year : 04.11.8927. 
 year-month-day : 2024-05-14. 
 year.day-of-year : 8927.308. 
 
 For the three with a month and a day, you can separate the parts with a dot, a slash or a dash—whichever you type is fine. 
 Before the zero point —if your calendar has dates before its year one, the word that marks them: BCE , BC , BBY , Before Landing . Then "12 BCE" is understood as twelve years before. Leave it empty for a calendar that only counts forward (a stardate, say). 
 The calendar also has a short key (shown when there's more than one calendar). It's what facts point at behind the scenes and doesn't change once set; the name is yours to change whenever you like. 
 Writing a date 
 Wherever the codex asks for a date—a fact's from and to , when an entry exists—type it the way the calendar says. The codex keeps exactly what you typed and shows it back the same way; underneath, it works out an order so it knows that 68 CE comes before 70 CE and 2 BCE before 1 CE. A bare year is always accepted, whatever the calendar's style, so "8927" works on a month.day.year calendar when you don't know the day. 
 If something can't be read, the box tells you and shows the style the calendar expects. (And yes: historians skipped year zero, and so does the codex—1 BCE is followed by 1 CE.) 
 A second calendar 
 Science fiction and fantasy often need two: the world's own reckoning and, thanks to time travel or prequels, the one the readers know. Click Add a second calendar in the Calendar system card, give it a name and a style, and it joins the first. Every fact's when then says which calendar it's on, and an entry can exist on more than one—a character might have a stellar-date birth and a Gregorian one. 
 One calendar is marked primary : it's the one offered first. Make primary changes which. 
 Where dates show up 
 
 On facts: Add book, series, or date-specific information lets a fact run from one date to another on a calendar. 
 On entries: each entry can say when it exists on each calendar, or Applies to all dates . An entry that doesn't exist yet at the moment you're writing in won't show up when the codex is framed to that moment. 
 In Working in : for each calendar in use, choose Any time , or At… a date, or Not on this calendar , and the whole codex shows the world as it was then. 
 
 Those three are the subject of What's true when and where .