Arabic date starts from Magrib (sunset). So it is 15th tonight here for me. You must check with your hijiri calander in your area.
As for the greatness of this night, I answered here. http://answers.yahoo.com/question/index;…
Yes, we don't celebrate this night nor we ignore the importance of this night.
Aboo Hurayrah, ‘Aa’ishah, and other companions (may Allaah be pleased with them) reported that the Prophet (peace be upon him) said: “Allaah looks upon His creation on the middle of the night of Sha’baan, and He forgives all of His creation, except for a mushrik or a quarreler.” (al-Majmoo’Recorded by al – Bazzaar, at – Tirmithee, and others. Classed as Saheeh by Sheikh al – Albaanee in as – Saheehah, Number 1144)
The Messenger of Allaah Sallallahu 'alayhi wa sallam said: "Allaah the Blessed and Most High looks to His creation on the middle night of Sha'baan and forgives all of His creation except for the one who ascribes partners to Him and the one who shows enmity."
(This is an authentic (saheeh) hadeeth. It is recorded by Ibn Maajah (no.1390), Ahmad (no.6642), Ibn Hibbaan (no.1980) and others from a group of Companions. It is authenticated by al-Haythamee in az-Zawaa'id (8/65) saying: "Reported by at-Tabaraanee in al-Kabeer and in al-Awsat and its narrators are trustworthy" and it is further authenticated by Shaikh al-Albaanee in as-Saheehah (no.1144)