You can actually find all these dates if you search the web. For reference sake, I'll just post them here anyway:

SZ is announced as a group and had press conference in Sep 29, 2011

Debut date: Nov 16, 2011

The date they joined the agency (each member)
Kento: Apr 20, 2008
Fuma: Apr 27, 2008
Shori: Oct 30, 2010 (Same day as his birthday)
Sou: Mar, 2011
Marius: Jan, 2011

1st single release: Nov 16, 2011
2nd single release: Apr 11, 2012
3rd single release: Oct 03, 2012
Album Release: Nov 11, 2012

Summary 2012 date: Aug 11, 2012 - Sep 02, 2012
Summary DVD release date: Feb 13, 2013

Birthdays (each member)
Kento: Mar 13, 1994
Fuma: Mar 07, 1995
Shori: Oct 30, 1996
Sou: Nov 27, 1997
Marius: Mar 30, 2000

1st concert: Tokyo- Feb 11-12, 2012 Osaka- Feb 18-19, 2012
Arena Con 2012: Tokyo - Mar 29-30, 2012 Osaka- Apr 01, 2012
1st concert DVD release date: Aug 15, 2012

New Year Arena Concert 2013: Jan 02-06, 2013

btw, their first photobook is released on Aug 01, 2012

and correction to the album release date, it's Nov 14

Edited at 2013-01-01 04:01 pm (UTC)

Thank you for asnwering ; u ; This was very helpful!

Birthday:
- Nakajima Kento: March 13, 1994
- Kikuchi Fuma: March 07, 1995
- Sato Shori: October 30, 1996
- Matsushima Sou: November 27, 1997
- Yo Marius: March 30, 2000

1st single release: 11.16.2011
2nd single release: 04.11.2012
3rd single release: 10.03.2012
Album release: 11.14.2012

First concert: 02.11.2012 - 02.19.2012
Summary 2012: 08.11.2012 - 09.02.2012

Joined agency [from Sexy Zone Special Interview]:
- Kento: April 20, 2008
- Fuma: April 27, 2008
- Shori: October, 2010
- Sou: February, 2011
- Marius: January, 2011

Debut date: 09.29.2011 (I'm not sure, sorry before)

Thank you for helping *u*