They have decided to make Pranab Mukherjee the Indian president with retrospective effect for the period 1995 - 2000!
(An original Vivekean quote/tweet)
Explanation: As this tweet confused people on twittersphere
Retrospective: Applying to the past (when not existing or applicable formerly.)
So, just as Vodafone did not have a tax liability for a particular period earlier but Pranab Mukherjee has arbitrarily now decided to tax them retrospectively for the said period. Similarly, we're now making him President retrospectively for the period 1995-2000 - a position he had not held earlier.