NREL has defined the procedures to derive solar radiation data for TMY. Details can be found here: http://rredc.nrel.gov/solar/old_data/nsrdb/1991-2005/tmy3/
For a typical monsoon nation like India, TMY could be taken from June to May. The India Meteorological Department (IMD) defines 4 Metorological seasons viz., (i) Southwest Monsoon Season: June - September; (ii) Post Monsoon Season: October - December; (iii) Winter Season: January – February and (iv) Pre Monsoon Season: March – May.
As the above answer from NRSC suggests, for India, TMY can be framed from June to May as seen from weather and agriculture ( based on rainfall seasons).
You can check the definition and methodological procedure to obtain a Typical Meteorological Year on this PhD dissertation: http://www.tdx.cat/bitstream/handle/10803/288372/TChS1de1.pdf?sequence=1 pages 38-41
The TMY is dened based on the Filkenstein-Schafer method, a statistical
method selecting the 12 representative months with minimum difference from the long-term conditions.
I suggest you start the Meteorological since the start of global geophysical changes in the northern hemisphere this year from the beginning of February. Then on the planet cyclical changes occurring in its vish structures, including the atmosphere.
I think something like Typical meteorological year is a collation of selected and representative weather data for a specific location, listing values of meteorological elements for a one-year period. The values are generated from a data bank much longer than a year in duration. It is specially selected so that it presents the range of weather phenomena for the location analyzed, while still giving annual averages that are consistent with the long-term averages for the location . TMY is widely used to simulate the thermal behavior of buildings, solar energy systems and many other applications