After idam 'this' ending in the Locative -7th case comes the affix rhil when time is denoted.,
The words सप्तम्याः and काले are understood. This rhil debars ha. The ल् of र्हिल् is for accent. Thus अस्मिन् काले = एतर्हि 5.3.4 'at this time'. Why 'when time is denoted'? Observe, इह 'in this place', as इह देशे ॥ See 5.3.4.,