message: validation: use std::chrono in IsCurrentForFeeEstimation()
diff: @@ -77,8 +77,8 @@ static const unsigned int UNDOFILE_CHUNK_SIZE = 0x100000; // 1 MiB
  static constexpr std::chrono::hours DATABASE_WRITE_INTERVAL{1};
  /** Time to wait between flushing chainstate to disk. */
  static constexpr std::chrono::hours DATABASE_FLUSH_INTERVAL{24};
  -/** Maximum age of our tip in seconds for us to be considered current for fee estimation */
  -static const int64_t MAX_FEE_ESTIMATION_TIP_AGE = 3 * 60 * 60;
  +/** Maximum age of our tip for us to be considered current for fee estimation */
  +static constexpr std::chrono::hours MAX_FEE_ESTIMATION_TIP_AGE{3};
  bool CBlockIndexWorkComparator::operator()(const CBlockIndex *pa, const CBlockIndex *pb) const {
  // First sort by most total work, ...
  