According to time period between two world cup there should be 4 years gap but last world cup played in 1996 (Asia), so why is that happen?
If you look at the time of year these world cups took place the time between them are almost comparible.
- 1975 (7 June - 21 June) England
- 1979 (9 June - 23 June) England
- 1983 (9 June - 25 June) England
- 1987 (8 October - 8 November) India, Pakistan
- 1992 (22 February - 25 March) Australia, NZ
- 1996 (14 February - 17 March) India, Pakistan, Sri Lanka
- 1999 (14 May - 20 June) England, Wales, Ireland, Scotland, Netherlands
- 2003 (9 February - 23 March) SA, Kenya, Zimbabwe
- 2007 (13 March - 28 April) WI
- 2011 (19 February - 2 April) India, Sri Lanka, Bangladesh
- 2015 (14 February - 29 March) Australia, NZ
As can be seen that the 1992 world cup was 4 years 3 months after the 1987 world cup. In Australia and NZ the best cricket weather is after the new year, so that is probablty why it appeared as 1992 and not late 1991.
Exactly 4 years later Sri Lanka held the world cup in 1996. If this was readjusted, again leaving only 3 years for them to host, which could have been too short
Thinking a bit more Sri Lanka's turn was correctly set at 1996 since it was held in February possibly for the same reasons as it was held in 1992 for Australia and NZ. They could have chosen October/November 1995 (as was the 1987 World Cup in India/Pakistan) but perhaps the weather was better in February 1996. Of course in western Europe mid year is the best time so May/June 1999 was logically the next time it would be held.
The 2003, 2011, 2015 World cups were in February but were correct and not offset by a year. The "heads up" of when these cups would start would give these hosts time to prepare and separate itself from the dates of the ICC Champions Trophies
Perhaps the change was down, not to the 1999 world cup, but the 1992 world cup. They probably wanted it to be 1991 but that would have meant February 1991 and not late 1991, which could have had issues with both NZ and Australia having enough time to get ready for the world cup. This was the first world cup that featured colored clothing and day-night matches.
They probably always wanted to get back on the orginal 4 year pattern laid out by the original first 4 world cups. and in fact they kinda did with those 2 being only 2 months into the following year.
Other possible factors
Another consideration was how close the ICC Trophy was to the World cup. It started out every 2 years, but later changed to every 4 years, ideally not the same year as the World cup:
- 1998 (24 October - 1 November) Bangaldesh (ICC Knockout Trophy)
- 2000 (3 October - 15 October) Kenya (ICC Knockout Trophy)
- 2002 (12 September - 30 September) Sri Lanka (ICC Champions Trophy)
- 2004 (10 September - 25 September) England (ICC Champions Trophy)
- 2006 (7 October - 5 November) India (ICC Champions Trophy)
- 2009 (23 September - 5 October) SA (ICC Champions Trophy)
- 2013 (8 June - 23 June) England, Wales (ICC Champions Trophy)
- 2017 (1 June - 18 June) England, Wales (ICC Champions Trophy)
As can be seen, the first was in 1998, 2 years 6 months after the previous cricket world cup. The hosting of the 1999 world cup would have been determined by then (and the date) so having it every 2 yrs since would not have caused any clash. You can also see they adjusted in 2009 (3 yr gap) which was caused by concern over pakistan security hosting the 2008 trophy. After that it became every 4 years and would fall right in the middle of the world cup cycle, which worked out quite well.
Another consideration perhaps is down to the 5 other major global sporting events and their dates (Summer and Winter olympics, Rugby World cup, Football (Soccer) World cup, Commonwealth Games), all of which are in 4 year cycles.
- Summer Olympics (...1988, 1992, 1996, 2000, 2004...)
- Winter Olympics (...1988, 1992, 1994, 1998, 2002...)
- Rugby World cup (...1987, 1991, 1995, 1999, 2003...)
- Football World cup (...1986, 1990, 1994, 1998, 2002...)
- Commonwealth Games (...1986, 1990, 1994, 1998, 2002...)
Note that the Rugby world cup and Commonwealth games features almost the same nations as the cricket world cup.
As you can see the "even" years are pretty jam packed so making it the "odd" makes sense, though they are the same years as the cricket world cup which could make planning harder so they don't happen at the same time.
Remember, all these tournaments take a lot of money to host and the TV rights, sponsor money and getting the people in are all important. Having the lesser sport of cricket not competing with the likes of the Summer Olympics would work in their favour.