엊그제 같은데 (It is just like yesterday) : This expression means that something which happened long time ago seems as if it just happened yesterday or the day before yesterday.
일상회화 (Korean Conversation)
When we feel like time flies, we use the expression “엊그제 같은데 (it seems like yesterday or the day before yesterday)”. It means something that happened so long ago but it seems to you that it just happened yesterday or the day before yesterday. It has a nuance that you feel little bit sad or surprised for the days going so quickly without noticing it.