The month before was Rajab, one of the 4 sacred months, much heavier then Shaban in scale because sins committed in the 4 sacred months are far worse than those committed in other months.
Dhul-Qaida, Dhul-Hija, Muharam (3 consecutive sacred months, then Rajab as seperate one.)
{Indeed, the number of months with Allah is twelve [lunar] months in the register of Allah [from] the day He created the heavens and the earth; of these, four are sacred. That is the correct religion, so do not wrong yourselves during them [at-Tawbah 9:36]