Refer to: click here
Introduced from 1st April, 1983 as a bi-weekly express between Howrah and New Jalpaiguri.
From 15th May, 1983 it was converted to a tri-weekly, and by end of 1984, its frequency was increased to 6 days a week.
Around 1989, the Howrah-New Bongaigaon Janata express and the New Jalpaiguri-New Bongaigaon Teesa-Brahmaputra express were merged with the Kanchenjunga express. Following this...
more...

rationalization of services, the Kanchenjunga express started running as a daily superfast train between Howrah and Guwahati. Shortly afterwards, it started originating from Sealdah instead of Howrah.
From 8th October, 2016, it was extended to Agartala twice a week. The frequency was increased to 4 days a week in July 2017.

Refer to: click here
Introduced from 1st April, 1983 as a bi-weekly express between Howrah and New Jalpaiguri.
From 15th May, 1983 it was converted to a tri-weekly, and by end of 1984, its frequency was increased to 6 days a week.
Around 1989, the Howrah-New Bongaigaon Janata express and the New Jalpaiguri-New Bongaigaon Teesa-Brahmaputra express were merged with the Kanchenjunga express. Following this...
more...

rationalization of services, the Kanchenjunga express started running as a daily superfast train between Howrah and Guwahati. Shortly afterwards, it started originating from Sealdah instead of Howrah.
From 8th October, 2016, it was extended to Agartala twice a week. The frequency was increased to 4 days a week in July 2017.

Refer to: click here
Introduced from 1st April, 1983 as a bi-weekly express between Howrah and New Jalpaiguri.
From 15th May, 1983 it was converted to a tri-weekly, and by end of 1984, its frequency was increased to 6 days a week.
Around 1989, the Howrah-New Bongaigaon Janata express and the New Jalpaiguri-New Bongaigaon Teesa-Brahmaputra express were merged with the Kanchenjunga express. Following this...
more...

rationalization of services, the Kanchenjunga express started running as a daily superfast train between Howrah and Guwahati. Shortly afterwards, it started originating from Sealdah instead of Howrah.
From 1st February, 2016, it was extended to Silchar for 3 days a week.

Refer to: click here
Introduced from 1st April, 1983 as a bi-weekly express between Howrah and New Jalpaiguri.
From 15th May, 1983 it was converted to a tri-weekly, and by end of 1984, its frequency was increased to 6 days a week.
Around 1989, the Howrah-New Bongaigaon Janata express and the New Jalpaiguri-New Bongaigaon Teesa-Brahmaputra express were merged with the Kanchenjunga express. Following this...
more...

rationalization of services, the Kanchenjunga express started running as a daily superfast train between Howrah and Guwahati. Shortly afterwards, it started originating from Sealdah instead of Howrah.
From 1st February, 2016, it was extended to Silchar for 3 days a week.

Source: An advertisement in the Times of India, dated December 6th, 1864. The full archive is available online on the British Newspaper archives ' website. - click here
Content from this website is copyrighted and cannot be reproduced without the necessary permissions. I'll share a scan of the relevant newspaper article when I get the permission.
As far as the history is concerned, the first train between Bombay and Ahmedabad was flagged off on Monday, 26th December, 1864.
At...
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the time of inauguration, the schedule was as follows:
Grant Road (Terminus in Bombay at that time) - 7 AM
Bulsar (Valsad) - 2:20PM
Surat - 5:10 PM
Passengers had to stop overnight at Surat and continue the journey from the next morning.
Surat - 7AM
Ankleswar - 8:47AM
Cross the Narmada river by a ferry and depart by train from Bharuch at 10:42AM.
Baroda at 1:24PM
Ahmedabad - 5 PM.
From June 1865, the train was sped up and started completing the journey in a single day, starting from Grant Road at 7AM and reaching Ahmedabad by 9PM.
From 15th October, 1878, the train was converted into an overnight train. In the later years, this overnight rain was sped up and named as the 'Gujarat' mail.