I'm not sure what's point of your question. The tense of sentence is determined by the tense of main verb. There are seven speech levels in Korean, and each level has its own unique set of verb endings which are used to indicate the level of formality of a situation. Here is a list of same word with different speech level in order of politeness present form (나는)먹어. (나는)먹는다. (나는)먹네. (나는)먹으오. (저는)먹어요. (저는)먹습니다. future form (나는)먹겠어. (나는)먹겠다. (나는)먹겠네. (나는)먹겠소. (저는)먹겠어요. (저는)먹겠습니다. past form (나는)먹었어. (나는)먹었다. (나는)먹었네. (나는)먹었소. (저는)먹었어요. (저는)먹었습니다.