"Ni" can not be replaced by "e" in all uses. It must be used with days of the week as in ("Nichiyoubi ni Kyoto ni ikimasu" "I will go to Kyoto on Sunday".) where "ni" is used both to mark the day of the week (日曜日) and the goal of the movement (京都). It is also required with numerical times (but not relative times). For example, "ni" must be used in the sentence ("Juu ichi ji ni nemasu" "I will go to sleep at 11 o'clock") to mark the numerical time (十一時) but it is not used with the relative time words like tomorrow (明日), yesterday (昨日), today (今日), last week (先週), next month (来月), etc. For example, in the sentence ("watashi wa kinou shigoto ni ikimasen deshita" "I did not go to work yesterday") no particle is needed for "yesterday" (昨日), but "ni" is used to mark the goal of movement (仕事に).