When there is uninterrupted access and use of light or air to and for any building have been peaceably enjoyed as an easement over a property belonging to the Government, the time period for this uninterrupted exercise of easementary right shall be?

S. 25. Acquisition of easements by prescription. (1) Where the access and use of light or air to and for any building have been peaceably enjoyed therewith as an easement, and as of right, without interruption, and for twenty years, and where any way or watercourse or the use of any water or any other easement (whether affirmative or negative) has been peaceably and openly enjoyed by any person claiming title thereto as an easement and as of right without interruption and for twenty years, the right to such access and use of light or air, way, watercourse, use of water, or other easement shall be absolute and indefeasible. (2) Each of the said periods of twenty years shall be taken to be a period ending within two years next before the institution of the suit wherein the claim to which such period relates is contested. (3) Where the property over which a right is claimed under sub-section (1) belongs to the Government that sub-section shall be read as if for the words "twenty years" the words "thirty years" were substituted.