This Manual of Style has the simple purpose of making things look alike — it is a style guide. The following rules don't claim to be the last word. One way is often as good as another, but if everyone does it the same way, the Ireland Information Guide will be easier to read and easier to use, not to mention easier to write and easier to edit.

New contributors are reminded that clear, informative and unbiased writing is always more important than presentation and formatting. Writers are not expected or required to follow all or any these rules: the joy of wiki editing is that perfection is not required. Copy-editing Ireland Information Guide users will be referring to these pages when weeding, and pages will be gradually made to conform with this guide.

Dates and times

Years, decades, centuries

A page title that is just a number is always a year. Pages also exist for days of the year, decades, centuries and even millennia. The formats for references to years are:

• 474
  • 474
• 474 BC (note no periods) or 474 BCE
  • 474 BC or 474 BCE
• 18th century (Note century is not capitalized. Note also that "1700s" is not a century, but a decade as illustrated below.)
  • 18th century
• 10th century BC or 10th century BCE
  • 10th century BC or 10th century BCE
• 1830s (note no apostrophe)
  • 1830s
• December 1983 (note that December is not linked)
  • December 1983
• 320s BC or 320s BCE
  • 320s BC or 320s BCE

Articles for the year 500 BC and earlier should be redirected to the relevant decade. Articles for the year 1700 BC and earlier should be redirected to the relevant century. Articles for the year 4000 BC and earlier should be redirected to the relevant millennium.

Note that the 1st century BC was from 100 BC–1 BC (there was no year 0) so 1700 BC would be the first year of the 17th century BC, 1800 BC would be the first year of the 18th century BC, etc. Similarly, 4000 BC was the first year of the 4th millennium BC, not the last year of the 5th millennium BC.

Eras

Both the BCE/CE era names and the BC/AD era names are acceptable, but be consistent within an article. Normally you should use plain numbers for years in the Common Era, but when events span the start of the Common Era, use AD or CE for the date at the end of the range (note that AD precedes the date and CE follows it). For example, 1 BC–AD 1 or [[1 BCE]]–1 CE.

In articles about prehistory, use BP (before present) or MYA (million years ago).

Dates

Dates should be wikified so that each reader sees the dates formatted according to their own preference. You should use one of the following formats:

Month Day, Year:

February 17

February 17, 1958

Day Month Year:

17 February

17 February 1958

YYYY-MM-DD (an ISO 8601 format):

1958-[[02-17]]

Importantly, if a date is to be recognised by the software, it must be "wikified", as shown above. An unlinked date such as "February 11, 1958" will not be converted. To create a date which is linked but not converted, use a link with alternate text, for example "February 17".

In article titles dates will not be converted. It's generally preferable to use the format used by local English speakers at the location of the event. For events within Europe and Oceania, that is usually 11 February 2004 (no comma). For the United States it's usually February 11, 2004 (with comma). Redirects for the other common forms should always be created.

Incorrect date formats

What not to do:

• Do not use numbers to express a month, except in full ISO 8601 format, which always includes the year. Always express a month as a whole word (e.g. "February") to avoid ambiguity. Please note that in the ISO 8601 format, a leading zero is always added to single-digit months and days.
• Do not link two digits to express a year unless discussing the years from AD 10 to AD 99. Ireland Information Guide deals with all of history, not just the last hundred years, so always use four digits for years and decades after AD 999. Using the less formal two-digit form for a decade within an article is acceptable when it does not create an ambiguity. For example, when referring to the decade of the 20th century known as the eighties, use 1980s or '80s, not just [[80s]].
• Do not use piped links to "years in music" or analogous pages (e.g. 1983). (See Ireland Information Guide:Wikiproject Music standards for discussion).
• In general, avoid using multiple date formats in the same article.

Note, however, that the content of a direct quotation — i.e., the word-for-word reproduction of a written or oral utterance — should not be altered to conform to the Ireland Information Guide "Manual of Style". In other words, a paragraph like the (fictional) one below is fine:

• Tony Blair, responding to critics within his party, said "The world has totally changed since the 11th of September." He was echoing earlier sentiments by Lord Ronald McDonald, who said that "nine-eleven was the day that the American public woke up to the reality of terrorism."

Dates of birth and death

• Charles Darwin (February 12, 1809 – April 19, 1882)
• Socrates (470–399 BC)
  • When only the years are known.
• Serena Williams (born September 26, 1981)
  • For a person still living at the time the article was written.
• Offa (died July 26, 796)
  • When the date of birth is unknown.
• Genghis Khan (c. 1162 – August 18, 1227)
  • When the date of birth is known approximately.
• Dionysius Exiguus (c. 470–c. 540)
  • When dates of birth and death are known approximately.
• Rameses III (reigned c. 1180–c. 1150 BC)
  • When only the dates of the reign are known.

Ranges of dates are given with a spaced or unspaced hyphen or en-dash (–). See Ireland Information Guide:Manual of Style#Dashes.

Calendars

You can give dates in any appropriate calendar, as long as you also give the date in either the Julian or Gregorian calendar, as described below. For example, an article on the early history of Islam may give dates in both the Islamic calendar and the Julian calendar.

• Current events should be given in the Gregorian calendar.
• Dates before the adoption of the Gregorian calendar on 1582-10-15 must be given in the Julian calendar and not converted.
• Dates of events in countries using the Gregorian calendar should be given in the Gregorian calendar. This includes much of Europe from 1582, the British Empire from 1752-09-14, Russia from 1918-02-14, and so on (see the Gregorian calendar article).

Other dates are ambiguous. Your options for this period are:

• Give the dates in the Julian calendar only. This means that the dates will match the dates in the primary sources for that period. If you do this you should indicate that the dates are in the Julian calendar.
• Convert the dates to the Gregorian calendar. This means that events in different countries can be correlated.
• Give dates in both calendars, for example:
  • 24 March 1602 (Old Style)/3 April 1603 (New Style)

Times

Times should be written in the 24-hour clock (HH:MM or HH:MM:SS). The 12-hour clock has a number of problems: it isn't used throughout the world; it often makes it harder to convert between different time zones; and "12:00 am" and "12:00 pm" are ambiguous.

Time zones

When writing a date, first consider where the event happened and use the time zone there. For example, the date of the Attack on Pearl Harbor should be December 7, 1941 (Hawaii time/date). If it is difficult to judge where, consider what is significant. For example, if some cracker in Japan hacked the Pentagon, use the time zone for the Pentagon.

If you know it, include the UTC date and time of the event in the article, indicating that it's UTC.

Style for numbers, weights, and measures

Very large numbers, such as pinball scores, should be divided up by commas every three places. (Note that this is different from SI notation where a thin space is used every three places.) In scientific contexts, scientific notation is preferred: see below.

A dot (period) "." should be used as the decimal point, separating the integer part from the fractional part.

The issue of whether all units should be metric (SI), Imperial, or American units is being debated at Ireland Information Guide:Measurements Debate. These points are mostly non-controversial:

• In scientific contexts, such as physics and chemistry, use SI units. Unless for any historic reference or other particular reason, it is not necessary to state American or Imperial units in parentheses.
• If using American or Imperial units, give the metric equivalent as a courtesy.
• If using metric units, remember that many readers will not know what you mean and will be aided by the equivalent in American or Imperial units.
• Equivalents should be given to the same level of precision as the original measurement, for example, "the moon is 250,000 miles (400,000 km) from Earth", not "402,336 km".
• If the quantity is always given in one form, you need not perform any conversion at all.

Use standard abbreviations/symbols for metric units and without 's' in the plural, m for metre, kg for kilogram, etc. (see SI for the list), and two-letter abbreviations for inch-pound units, in=inch (not "), ft=foot (not '), yd=yard (not yds), mi=mile, lb=pound (not lbs), gal=gallon, pt=pint, qt=quart, and so forth. Where possible, use the symbols with unit combinations, for example use ft/s rather than fps. The terms fluid ounce, pint, quart, gallon and barrel are ambiguous units so you need to specify the unit more precisely. You may assume that ounces and pounds are Avoirdupois unless otherwise indicated.

Measurements (both number and unit together) of dimensions with existing orders of magnitude pages should be linked to the appropriate page.

Speed should be given in m/s by default, but in km/h when this is conventional (speed limits, etc.).

Areas of land should be given in km², which is entered as km&sup2;. This form is preferable to km², which adds extra line leading. Smaller areas in m² etc. Volumes in m³, cm³ etc. Note that the compact superscript style works only for 1, 2 and 3 (unless you use numeric UTF-8 codes &8304; for superscript zero and &8308; to &8313; for superscript 4 to 9). This means that the <sup> style has to be used when general superscripts are required, as in the examples below.

When describing areas of agriculture, forests, parks, wilderness, etc., hectares are an acceptable (not mandatory) alternative to km².

Use a non-breaking space character between the value and its units: thus 25&nbsp;lb and not 25 lb or 25lb. This will prevent word-wrapping from inserting a line break between the number and the unit.

Examples

• The highest score recorded for the Deuces High pinball game was 11,933,750.
• The hippopotamus stands 1.5 m (5 ft) at the shoulders and weighs between 2700 and 4500 kg (roughly 6000 to 10000 lb).
• The first sub-four-minute mile was run by Roger Bannister.
• The 155 mm diameter projectile offers a wide range of options for battlefield usage.
• 10² = 100
  • 10&sup2; = 100
• A large number such as 156,234,000,000,000,000,000,000,000,000 can be concisely recorded as 1.56234×10²⁹, and a small number such as 0.0000000000234 can be written as 2.34×10^-11.
  • A large number such as 156,234,000,000,000,000,000,000,000,000 can be concisely recorded as 1.56234&times;10²⁹⁷, and a small number such as 0.0000000000234 can be written as 2.34&times;10^-11.

See orders of magnitude and the talk page there for ongoing, possibly resolved debate on which style of exponent notation to use for large numbers.

Number names

• In a non-technical context, and with the exception of displaying tabulated data, the words per cent (or percent if you're using American English) should be written out in full, rather than using the % symbol.

• Whole numbers between zero and ten should be spelt in full. Numbers higher than ten may be represented by numerals, except where they appear as the first word in a sentence, in which case they should be written out in full.

• Recently, people have disagreed whether a billion is 10⁹ or 10¹², and in Spanish, French, Norwegian, Polish and German the word stands for the latter — which was also the original English [until when?] usage. Prefer avoiding these names altogether, or at the very least explain it at its first occurrence in an article. The same problem arises with other numbers in the ~illion family greater than a million. See detailed discussion in Number names.

Natural number

Natural number has two meanings:

• positive integer
• non-negative integer (i.e. including zero)

Except where it does not matter which is chosen, explicitly use one of the above instead of natural numbers.

In Ireland Information Guide, "natural number" unequivocally means "non-negative integer", as the natural number article explains. So if you link to the natural number article, it's clear what you mean.

Ranges

Sometimes numbers and dates are expressed in ranges, such as "4–7" for the numbers 4 through 7. Use an en dash for these when possible. See Ireland Information Guide:Manual of Style#Dashes for more information.