一天不一天+A    The construction “一天比一天+A”

     The construction “一天比一天+A” means “day by day; the more …… the more……”, which is used as an adverbial to indicate a comparison. Similar to “越来越”, it shows that something intensifies with the passage of time, for example,
     你做饭技术一天比一天好。
     大家手里的钱一天比一天多了。
     他的身体一天比一天差。