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5.1.3.4 Appearance factor of days

An appearance factor of days is used to define a concrete displacement of recurrent fixed dates.

An appearance factor of days (‘.n’) is specified by a ‘.’ character and must trail the day field —which must have a concrete value in a date part of a Gcal resource file and has not been set to a zero value— respectively either lead or trail a repetition factor of days. Except fixed dates which occur only on a definite weekday and are not specified by using a range of days, like ‘199600mon Every Monday 1996’, such an appearance factor may be specified in all possible codings of date parts of a Gcal resource file. This factor may be specified with each single element of lists of days, but in a range of days, this factor may trail only the final day of the range. Well, the use of such an appearance factor is only helpful if it is either given in a range of days, or if it is given together with a repetition factor.

This factor may have values in range 1...999. Fixed dates will be ignored if the factor takes values greater than the real difference between the date of the occurrence of the fixed date and the last day of the year, respectively the end of the period, for which the fixed dates shall either be produced or respected.

Assuming a fixed date shall always occur on the 15th day in every month of the year 1996 and covers a period of seven days (inclusive the 15th itself), but shall only be respected every third day (i.e. two days have to be skipped at a time) within this period, e.g. ‘Training-college’, one solution would be on the one hand a fixed date entry in the resource file for the 15th of the month, for the 18th and for the 21st of the month, which would be a total of three entries in the resource file for such a fixed date1.

On the other hand, this expense can be reduced to a total of only one entry in the resource file by using an appearance factor of days, which is likewise valid for the 15th, the 18th and the 21st in every month, namely on the one hand by the use of a repetition factor

     19960015:7.3 Training-college

or on the other hand by the use of a range of days

     19960015#21.3 Training-college

The use of appearance factors of days in the date part is permitted as follows:

Some examples to this:

000001fr3:11.3
In every year in January: every day that appears within the period of the 3rd Friday of the month and the succeeding ten days, but only every 3rd day within this period (skip two days at a time).
00000112:3.2
In every year in January: every day that appears within the period of the 12th of the month and the succeeding two days, but only every 2nd day within this period (skip one day at a time).
00000112:3.2,fr3:5.3
In every year in January: every day that appears within the period of the 12th of the month and the succeeding two days, but only every 2nd day within this period (skip one day at a time), and that appears within the period of the 3rd Friday of the month and the succeeding four days, but only every 3rd day within this period (skip two days at a time).
0*d1:10.1
In every year: every day that appears within the period of the 1st day of the year and the succeeding nine days, and this for any day within this period (skip zero days at a time).
0*d1:2.5
In every year: every day that appears within the period of the 1st day of the year and the succeeding day, but only every 5th day within this period (skip four days at a time). Well, the succeeding days (only one in this example) of the starting day (1st day of year) are not respected, because the next day resulted by the appearance factor exceeds the final day (resulted by the repetition factor) of the period.
0*d99fr:333.61
In every year: every day that appears within the period of the last Friday of the year and the succeeding 332 days, but only every 61st day within this period (skip 60 days at a time). Well, in cases a fixed date exceeds the year bounds, it will only be produced until the last day of the year. No succeeding day (332 in this example) of the starting day (last Friday of the year) is respected by reason of the displacement value of 60 days, because the next day resulted by the appearance factor exceeds the final day (resulted by the repetition factor) of the period (the last day of the year).
1996*w1fr:17.8
In the year 1996: every day that appears within the period of the Friday of the 1st week and the succeeding 16 days, but only every 8th day within this period (skip seven days at a time).
0@a:4.3
In every year: every day that appears within the period of the date of the date variable a and the succeeding three days, but only every 3rd day within this period (skip two days at a time).
1996@e-3:9.4
In the year 1996: every day that appears within the period of the date three days before the Easter Sunday's date and the succeeding eight days, but only every 4th day within this period (skip three days at a time).
1996@e3#-20sun.15
In the year 1996: every day that appears within the period of the date three days after the Easter Sunday's date until the 20th Sunday before the Easter Sunday's date, but only every 15th day within this period (skip 14 days at a time).
1996@t3#-20sun.15
In the year 1996: every day that appears within the period of the date three days after today's date until the 20th Sunday before today's date, but only every 15th day within this period (skip 14 days at a time).

Footnotes

[1] Apart from the possibility, that a list of days can be used in such a case.