User:OrenBochman/Chronology and Time

Chronological items*

Precise language*

Avoid statements that will age quickly (recently, soon, now) unless their meaning is fixed by the context; avoid relative terms such as currently (usually redundant), and in modern times. Instead, use either (i) more precise and absolute expressions (since the start of 2005; during the 1990s); or (ii) an as of phrase (as of August 2007).*

Times*

Context determines whether the 12- or 24-hour clock is used; in both, use colons as separators (1:38:09 pm, 13:38:09).

• 12-hour clock. 2:30 p.m. or 2:30 pm, spaced, preferably with  . Noon and midnight, not 12 pm and 12 am; specify whether midnight refers to the start or the end of a date unless it is clear.
• 24-hour clock. No am, pm, noon or midnight suffixes. A leading zero is optional (08:15 or 8:15). 00:00 is midnight at the start of a date, and 24:00 at the end.

Dates*

• Day-month or month-day? The rules for choosing between these two standard formats are here.
• Linking and autoformatting. Chronological items are not normally linked (not 1990s or 20th century), and autoformatting links for dates are now deprecated (not October 5, 2006).
• Suffixes, articles and commas. Don't use ordinal suffixes or articles, or put a comma between month and year: 14 February, not 14th February or the 14th of February; October 1976, not October, 1976 or October of 1976.
• Ranges. Minimize repetition, using an unspaced en dash where the range involves numerals alone (5–7 January 1979 or January 5–7, 2002) or a spaced en dash where opening and/or closing dates have internal spaces (5 January – 18 February 1979 or January 5 – February 18, 1979).
• Slashed. the night of 30/31 May—use rarely.
• Yearless. March 5—give the year unless it's obvious (March 5, 1956).
• ISO dates. Generally avoid ISO 8601 format (1976-05-13) in running prose. However, it may be useful in long lists and tables for conciseness.* [Under discussion, MOSNUM]

Longer periods*

• Months. Write as whole words (February, not 2). Use abbreviations such as Feb only where space is extremely limited, such as in tables and infoboxes.
• Seasons as dates. The seasons are reversed in each hemisphere; use neutral wording (in early 1990, in the second quarter of 2003, not summer 1990 or Spring 2003), with obvious exceptions such as the autumn harvest and mid-spring migration.
• Years
  • Redundancy. Not the year 1995, but 1995, unless it would be unclear.
  • Ranges. Like all ranges, separate with an en dash, not a hyphen (2005–08, not 2005-08). A closing CE/AD year is normally written with two digits (1881–86) unless in a different century (1881–1912). The full closing year is acceptable, but abbreviating it to one digit (1881–6) or three (1881–886) is not. Closing BCE/BC years are given in full (2590–2550 BCE). While one era signifier at the end of a date range still requires an unspaced en dash (12–5 BC), use a spaced en dash when the range crosses the eras (5 BC – 29 AD).
  • Slash. A slash can indicate regular defined yearly periods that don't coincide with calendar years (the financial year 1993/94).
• Eras
  • Which system? AD and BC are traditional, although CE and BCE are increasingly common. WP has no preference, but don't (i) mix the systems in an article, (ii) use them unless the era would be unclear, or (iii) insert conversions.
  • Formatting. Upper case, undotted and spaced (usually a hard-space): 2500 BCE.
  • Placement. Either AD 106 or 106 AD, but the other abbreviations appear after (106 CE, 3700 BCE, 3700 BC).
  • Long ago. On first occurrence, spell out and link abbreviations such as BP (before present), ka (kiloannum), kya (thousand years ago), Ma (mega-annum), Mya (million years ago), and Ga (giga-annum or billion years ago).
  • Approximations. c. and ca. indicate around, approximately, or about. They are spaced (c. 1291). Use a question mark instead (1291?) only if the date is questioned by the sources, rather than approximate.
• Decades. No apostrophe (the 1980s, not 1980's); use the two-digit form (the 80s, the '80s) only where the century is clear.
• Centuries. Use ordinal numbers, without superscripts: the 19th century, 19th-century opera (not 19^th).

Discussion

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