What would be a reason for irregular intervals of price registration? Could it be that the pricing changed by McDonalds at this interval and wouldn't the datase

What would be a reason for irregular intervals of price registration? Could it be that the pricing changed by McDonalds at this interval and wouldn't the dataset be more complete to include the months in which the price of the Big Mac didn't change? 2000-04-01 2001-04-01 2002-04-01 2003-04-01 2004-05-01 2005-06-01 2006-01-01 2006-05-01 2007-01-01 2007-06-01 2008-06-01 2009-07-01 2010-01-01 2010-07-01 2011-07-01 2012-01-01 2012-07-01 2013-01-01 2013-07-01 2014-01-01 2014-07-01 2015-01-01 2015-07-01 2016-01-01 2016-07-01 2017-01-01 2017-07-01 2018-01-01 2018-07-01 2019-01-01 2019-07-09 2020-01-14