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Dates are a vital part of family research, so accurate reporting of dates is very important. TNG follows the internationally accepted standards for date entry and the use of date modifiers to clarify uncertain dates.

If you enter a person into your TNG database, you must have some sort of evidence that they existed and should enter at least a birthdate, and a death date if your know they are no longer alive. No matter how uncertain you are of those dates, date modifiers allow you to frame the boundaries of your uncertainty.

For example, you know your Dad had a Mom, but have no idea when this Grandma of yours was born or when she died. You do know the year your Dad was born, 1931. Well, Grandma must have been at least ten years old when your Dad was born, so you can state her birthdate was before 1921 (BEF 1921). She died either in the same year your Dad was born or in the years after, so you give her death date as after 1930 (AFT 1930).

TNG Dates

Always enter dates in the standard genealogical format, DD MMM YYYY (for example, 22 Mar 2011).
Internally, TNG keeps dates in 50 character strings, allowing for date 'modifiers'.

Date Modifiers

TNG allows the use of the eight standard genealogy date modifiers as proscribed in the GEDCOM 5.5 release|:  ABT, CAL, EST, AFT, BEF, BET, FROM, TO and the term Y. (See below.)
(For date and date modifier abbreviations in German see Inputting Dates - Eingabemoeglichkeiten)

Upper / Lower Case in Dates

When entering event dates in TNG, the letters used for the month and the date modifiers may be any combination of upper and lower case letters (for example, Aug, Cal, aug, cal, AUG, CAL).
When displaying event dates TNG leaves the letters in the case in which you originally entered them, but always converts the letters to all capitals when performing internal calculations.
If you are considering creating new TNG php procedures which involve handling dates, be sure to wrap them in the php UCASE function (for example, UCASE(birthdate)).

Uncertain Dates

If you are sure an event occurred, but not sure of the exact date on which that event occurred, you may qualify the date you supply with one of the date approximation modifiers:  ABT, CAL, or EST (for example, Abt 12 Nov 1891; or, Abt Nov 1891; or, Abt 1891).
If you are sure an event occurred, are not sure of the exact date, but are sure of the range of dates, you may supply the known range by enclosing dates using BET date AND date (for example, BET 1845 AND 1851).

Ongoing Dates

Dates are sometimes used to describe ongoing conditions or circumstances occurring over more than one specific day. These dates may be entered using the FROM and/or TO date modifiers (for example, FROM 3 Apr 1901 TO 31 Mar 1911).
These date modifiers also allow for open-ended dating (for example, FROM 1835).

Calendar Changes

The calendar changed from the "Old Style" Julian Calendar to today's Gregorian Calendar starting 1582 ('mainland' Europe) and 1752 (Britain and North America).
If the event you are entering occurred during or before 1752 (Britain and North America) or 1582 (Europe) you must be very careful when entering the date; spend some time researching the Gregorian Calendar first.

Date Unknown

unknown is not acceptable as a date modifier when entering dates in any standard genealogical context, including the TNG environment. Don't use it when asked for a date in TNG. In every case you should be able to choose a suitable date modifier as described above, even if it's as wildly vague as BEF 2011!
If you're absolutely unable to estimate a date, but know the event happened, the designers of the GEDCOM standard suggest you use the date modifier Y as explained in the following excerpt:

The meaning of a GEDCOM tag without a value on its line depends on its subordinate context for any assertions intended by the researcher. For example, In an event structure, a subordinate DATE and/or PLACe value imply that an event happened. However, a subordinate NOTE or SOURce context by themselves do not imply that the event took place. For a researcher to indicate that an event took place without knowing a date or a place requires that a Y(es) value be added to the event tag line. Using this convention protects GEDCOM processors which may remove (prune) lines that have no value and also no subordinate lines. A N(o) value must not be used on an event tag line to assert that the event never happened.

There is some doubt that the procedures that examine and work with dates in the current version of TNG (8.1) recognize Y in its 'null' date modifier role.

GEDCOM Date Modifier Descriptions

excerpted from http: // www. gedcom . net/0g/gedcom55/55gcint.htm (site deleted):


ABT date
CAL date
EST date


ABT =About, meaning the date is not exact.
CAL =Calculated mathematically, for example, from an event date and age.
EST =Estimated based on an algorithm using some other event date.


ABT 1871
CAL 21 Sep 1799
EST Apr 1913


FROM date
TO date
FROM startdate TO enddate


FROM =Indicates the beginning of a happening or state.
TO =Indicates the ending of a happening or state.


From 1904 to 1915 =The state of some attribute existed from 1904 to 1915 inclusive.
FROM 1904 =The state of the attribute began in 1904 but the end date is unknown.
TO 1915 =The state ended in 1915 but the begin date is unknown.


BEF date
AFT date
BET startdate AND enddate


AFT =Event happened after the given date.
BEF =Event happened before the given date.
BET =Event happened some time between date 1 AND date 2. For example, bet 1904 and 1915 indicates that the event state (perhaps a single day) existed somewhere between 1904 and 1915 inclusive.
The date range differs from the date period in that the date range is an estimate that an event happened on a single date somewhere in the date range specified. The following are equivalent and interchangeable:
Short form  Long Form
----------  ---------
1852        BET 1 JAN 1852 AND 31 DEC 1852
1852        BET 1 JAN 1852 AND DEC 1852
1852        BET JAN 1852 AND 31 DEC 1852
1852        BET JAN 1852 AND DEC 1852
JAN 1920    BET 1 JAN 1920 AND 31 JAN 1920

Inputting Dates in Multi-Language Environment

See Inputting Dates - Eingabemoeglichkeiten on guidelines for inputting dates in a multi-language environment.