The Raag Time Cycle

In Hindustani classical music, each raag is rendered only at a specific time. The time of the raag depends on the vaadi swar and the anuvadi swars . This is so as each raag with it's particular swar is more effective if performed at a particular time. It is supposed to enhance the ras (mood) of the raag that the artiste is responsible for evoking.

But,some raags are seasonal in nature. For example raags that belong to the Malhar category can be sung at any time during the mansoon season. The traditional associations with respect to the season are - Monsoon - Raag Megh, Autumn - Raag Bhairav, Winter - Raag Malkouns, Spring - Raag Hindol.

For an image of Raag time cycle (Raag Samay Chakra)
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The 24 hours of a day are divided into 2 parts 
1> From 12 P. M. to 12 A.M.--This is called Poorva Bhaag and raags sung in this period are called poorva raags.
2> From 12 A.M. to 12 P.M.--This is called Uttar Bhaag and the raags in this period are called uttar raags.

The part of the saptak(octave) from Sa to Ma (sa re ga ma ) is called poorvang (earlier part) of a raag and from Ma to taar saptak Sa (pa dha ni sa) is called uttarang (later part) of the raag.

Poorvang Vaadi raag : The raags in which the vaadi swar lies in the poorvang are called poorvang vaadi raag. These raags are rendered in the poorva bhag of the day i.e. 12 A. M. to 12 P.M.

Uttarang Vaadi raag : The raags in which the vaadi swar lies in the poorvang are called poorvang vaadi raag. These raags are sung in the poorva bhaag of the day i.e. 12 P. M. to 12 A.M.
So if we know a vaadi swar of the raag we can estimate the time the raag will be rendered.
The raags in Hindustani classical music are divided in to 3 categories taking into account their swar (notes)--whether komal or teevra and samay(time)

1 : Raags with Komal Re and Komal Dha :

The sandhi prakaash  (dawn and dusk time) raag:
These again falls into 2 categories

a : pratah kaalin sandhi prakaash raag : raags sung at dawn
b: saayam  kaalin sandhi prakaash raag : raags sung at dusk

In sandhiprakaash raags ma plays very important role.
Most of pratah kaalin sandhi prakaash raags (dawn time) take the shuddha ma
Ex . raag Bhairav
Most of the sayam kaalin sanhdi prakaash raags(dusk time) take  teevra ma.
Ex : raag Maarva
Also, in most of the sandhiprakaash raags, Re is komal and Ga, Ni are shuddha. Dha can be komal or shuddha.

2 : Raags with shuddha re and shuddha dha:

The time at which these raags are rendered is after the sanhdi prakaash raags. They belong  mainly to Kalyan, Bilaval, Khamaaj thaat.
After the pratah kaalin sandhiprakaash raags the influence of shuddha Re and shuddha Dha starts rising. Hence the raags of this category are rendered from morning 7.00 to morning 10.00 and from evening 7.00 to evening 10.00
In this category Ga is essentially shuddha.
In the morning 7.00 to 10.00 category shuddha ma is prominent Ex.: Bilaval, Deskaar, Todi
In evening 7.00 to 10.00 category teevra ma is prominent Ex.: Yaman, Shuddha Kalyan, Bhoopali

3 : Raags with komal Ga and Komal Ni :

These raags are sung after the shuddha Re and shuddha Dha raags. They are sung from morning 10.00 to afternoon 4.00 eg. : Aasaavari, Jounpoori and night 10.00 to dawn 4.00 eg. : Bageshree, Jayjayvanti, Malkouns
In these raags Ga will surely be komal , the Re and Dha can be shuddha or komal.

Importance of Ma (Maddhyam) with regard to the time of the raag.

Normally , in the morning time raags shuddha Ma is prominent. In the raags with Komal Re and Komal Dha if shuddha Maddhyam is prominent then they are called Pratah Kaalin Sandhi Prakash raag.
In the evening raags teevra Madhyam is prominent. Thus in the evening with the raags such as Poorvi, Shree, Multaani, teevra Maddhyam comes into use which goes on till the 2nd prahar of the night. At that time with raags such as Bihaag, shuddha Madhyam starts getting prominence.

In the Pratah Kaleen Sandhi Prakash Raag the raags with the shuddha Madhyam ( Raag - Bhairav, Kalingada)  come first followed by raags with both the Maddhyam although Shuddha Maddhyam is prominent. (raag - Ramkali, Lalit)

After this is the time to sing raags with Shuddha Re and Shuddha Dha.. In these also Shuddha Maddhyam is prominent.( Raag Bilaval)

Then comes the time for Komal Gandhar raags. In this both the maddhyams are used. In some of them shuddha Maddhyam assumes prominence whereas in others teevra Maddhyam assumes prominence.

Introduction

Saptak (The Scale)

The Drone

Thaat

Today's form of Raag

The meaning of Alaap

The meaning of Taan

Raag Samay Chakra

Difference between Raag and Thaat

Ornamental Melody

Raag and Ras(Emotion)

Raag formation rules

Similarities and differences in Raags

Origin of Raag Names

The general Schema of raag Presentation

The Notation System

40 Principles of Indian Classical Music