|Duration (Tropical, Western)||21 June – 22 July (2014, UTC)|
Cancer (♋) is the fourth astrological sign, which is associated with the constellation Cancer. It spans the 90-120th degree of the zodiac, between 90 and 125.25 degree of celestial longitude. Under the tropical zodiac, the Sun transits this area on average between June 22 and July 21, and under the sidereal zodiac, the Sun transits this area between approximately July 16 and August 15.
In astrology, a decan is said to be the ensign for a set of days within the heliocentric phase of Cancer. Each paradigm has its own planetary liaison. All of this has to do with what planet is affecting the sun's path at the time.
Decan I: June 22 - July 1 (Sovereign: the Moon) "the positive and negative traits of this sign would be more prominent."
Decan II: July 2 - July 12 (Sovereign: Mars/Pluto) "the stronger qualities of the Zodiac Sign Cancer are generally exhibited in these individuals"
In astrology, a planet's domicile is the zodiac sign over which it has rulership. The planet said to be ruler of Cancer is the Moon.The term domicile also applies to the House in which a planet rules. Domicile is from the Latin domicilium whose root means house. The Domicile, or House, of the Moon is the 4th House of one's natal chart. 
- GaneshaSpeaks.com (http://www.ganeshaspeaks.com/cancer/cancer-decans.action); SiddhiVinayak Astrology Services
- Heindel, Max (1919), Simplified Scientific Astrology: A Complete Textbook on the Art of Erecting a Horoscope, with Philosophic Encyclopedia and Tables of Planetary Hours (4 ed.), Rosicrucian Fellowship, OCLC 36106074