def date_search(df, unix_ts_date):
  """!
  Create a filtered DataFrame that only contains entries that occurred on or
  past the specified date.

  @param df DataFrame: contains the readings from the sensor
  @param unix_ts_date Integer: the universal unix time of the starting date from
                               which to examine the data

  @return Return a Dataframe that only contains entries that occurred on or
          past the specified date.
  """

  filtered_df = df.loc[df['Ts'] >= unix_ts_date]
  return filtered_df