求助分析一段英语的一些疑问After the first fortnight or three weeks of her

求助分析一段英语的一些疑问
After the first fortnight or three weeks of her absence,health,good humour,and cheerfulness began to re-appear at Longbourn.Everything wore a happier aspect.The families who had been in town for the winter came back again,and summer finery and summer engagements arose.Mrs.Bennet was restored to her usual querulous serenity,and by the middle of June Kitty was so much recovered as to be able to enter Meryton without tears; an event of such happy promise as to make Elizabeth hope that by the following Christmas,she might be so tolerably reasonable as not to mention an officer above once a day,unless,by some cruel and malicious arrangement at the War-Office,another regiment should be quartered in Meryton.
The time fixed for the beginning of their Northern tour was now fast approaching; and a fortnight only was wanting of it,when a letter arrived from Mrs.Gardiner,which at once delayed its commencement and curtailed its extent.Mr.Gardiner would be prevented by business from setting out till a fortnight later in July,and must be in London again within a month; and as that left too short a period for them to go so far,and see so much as they had proposed,or at least to see it with the leisure and comfort they had built on,they were obliged to give up the Lakes,and substitute a more contracted tour; and,according to the present plan,were to go no farther northward than Derbyshire.In that county,there was enough to be seen to occupy the chief of their three weeks; and to Mrs.Gardiner it had a peculiarly strong attraction.The town where she had formerly passed some years of her life,and where they were now to spend a few days,was probably as great an object of her curiosity,as all the celebrated beauties of Matlock,Chatsworth,Dovedale,or the Peak.
这是《傲慢与偏见》里的两段话.里面的时间关系实在搞不清楚,第一段里说话的背景时间是六月在旬了.后面一段说他们计划北上旅游的时间快到了,只有两个星期了,也说是说基本上就到了七月份了.而里面的那封信又说,由于嘉丁纳先生因故要推迟选项两个星期,那不就等于说原有还剩下的两个星期加上又要推迟的两个星期,就要四个星期之后才能出发吗?那不到差不多到了七月下旬了吗?不推迟的行期本来也要到七月份了,而里面信上说的要推迟两个星期到七月份怎么解释呢?还有下面说的他们行期会很短,只有短短三个星期的行程,这又是从哪显示的,从哪个时间,到哪个时间呢?里面说的嘉丁纳先生一个月内还到到伦敦,这一个是从哪到哪的一个月?总之对这里面的时间关系我越看越糊涂,