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We present results from extensive broadband follow-up of GRB 210204A over theperiod of thirty days. We detect optical flares in the afterglow at 7.6 x 10^5s and 1.1 x 10^6 s after the burst: the most delayed flaring ever detected in aGRB afterglow. At the source redshift of 0.876, the rest-frame delay is 5.8 x10^5 s (6.71 d). We investigate possible causes for this flaring and concludethat the most likely cause is a refreshed shock in the jet. The prompt emissionof the GRB is within the range of typical long bursts: it shows three disjointemission episodes, which all follow the typical GRB correlations. This suggeststhat GRB 210204A might not have any special properties that caused late-timeflaring, and the lack of such detections for other afterglows might beresulting from the paucity of late-time observations. Systematic late-timefollow-up of a larger sample of GRBs can shed more light on such afterglowbehaviour. Further analysis of the GRB 210204A shows that the late time bump inthe light curve is highly unlikely due to underlying SNe at redshift (z) =0.876 and is more likely due to the late time flaring activity. The cause ofthis variability is not clearly quantifiable due to the lack of multi-band dataat late time constraints by the bad weather conditions. The flare of GRB210204A is the latest flare detected to date.

The long-active afterglow of GRB 210204A: Detection of the most delayed flares in a Gamma-Ray Burst