They are Islamic lunar months where the migration of the prophet to Medina started at the first month of them.

The Sacred Months

Written by Islamstory Monday, 26 March 2012
It is with the wisdom of Allaah that He favored some months over others, like favoring the month of Ramadhaan over all other months, because it is the month of mercy, the month of Quran, the month of forgiveness and freeing people from the Fire. It is a month which people glorified during the pre-Islamic period as well, and after Islam it became even more glorified.
 

Monthof Shawwal

Written by Islamstory Wednesday, 14 March 2012
Shawwal means lift or carry. Shawwal is the tenth month on the Lunar Islamic calendar. The first day of Shawwal is Eid ul-Fitr. There are also six days of fasting during Shawwal which, together with the Ramadan fasts, are equivalent to fasting perpetually.
   

Thesignificance of Muharram

Written by Islamstory Wednesday, 14 March 2012
Many rewards and blessings can be gained throughout the Islamic year, not only in Ramadhaan. Observing supererogatory fasts during Muharram is upheld by the prophet Muhammad.
 

The excellence of the month of Rajab

Written by Islamstory Sunday, 05 December 2010
Rajab is the seventh month in the Islamic lunar calendar. This month was regarded as one of the sacred months (Al-Ashhur-al-hurum) in which battles were prohibited in the days of the Holy Prophet (PBUH).
   

The excellence of the month of Sha'ban

Written by Islamstory Sunday, 05 December 2010
Sha'ban is the name of the eighth month of the Islamic lunar calendar, and it is so called because in this month the Arabs used to disperse (tasha'aba) in search of water, or it was said that it is so called because it sha'aba (branches out or emerges) i.e., it appears between the months of Rajab and Ramadan.
 

The excellence of the month of Safar

Written by Islamstory Sunday, 05 December 2010
The month of Safar is one of the twelve Hijri months, and it is the month which comes after Muharram.  Some of scholars said that it is so named because of the emptying (isfaar) of Makkah (i.e., its people would all leave) when they traveled during this month. It was also said that this month is named Safar because they used to raid other tribes at this time, and they would leave those whom they encountered bereft of their possessions (sifran min al-mataa’) – i.e., they would take all their belongings away and they would leave them with nothing.