The TMC was founded on January 1, 1998.
"The journey which began on January 1, 1998 has been full of struggles, but we have been steadfast in our resolve to fight for the people #Trinamool21," Banerjee said in a tweet.
"We are thankful to Maa-Mati-Manush for their constant support. And the workers who work hard 365 days a year for the people. A big salute to you," she said.
The TMC leadership had last week issued instructions to conduct various programmes across the state on Tuesday to mark the occasion.
The district leaders have arranged for party flag-hoisting programmes and street corner meetings to discuss and highlight achievements of the party in the last six-and-a-half years.
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