Oracle / SQL：将日期和时间连接到单个日期值时的无效数字格式模型

I am trying to create a trigger in Oracle that compares two dates and then deletes records if the difference of the two dates falls below a certain value. I have a full date value with the format 'DD-MON-YYYY HH24MI' and then for the second date value, I want to concatenate a 'DD-MON-YYYY' value with a 'HH24MI' value.I am trying to create a trigger in Oracle that