Hi Finnie,
Thomas has answered for me your question. Thanks Thomas
Let me put it this way. If after ROM and before your AD, both of you decided to split, it is still considered a divorce right? In the old days, there is no such thing as ROM. Everything is done in 1 day, hence AD is important. BUT that is the past...we are now into 21st century. And now, wedding is split in ROM and AD. As Thomas had mentioned, ROM is the day both of you officially and legally become husband and wife. AD is just a tea ceremony and banquet. So, if you think from this perspective, which do you think is more important?
Anyway, regardless of which is more important, as Chinese, we want good dates for everything. So if you can, choose auspicious dates for both!
You can get married in 7th month or Qing Ming, nothing will happen. Date selection does not take into account chinese culture. But i will generally avoid choosing dates in these months unless you specifically want to do it and let me know. Reason being so far, even if both of you agree to do it in 7th month, 99% of the time, your parents will not agree to it. So if you really want to do it in 7th mth, get the approval from your parents first before choosing. It will save you headaches next time
An auspicious date is basically a date whereby the Qi for the day is good and favourable for both of you, in according to both your Bazi. Everyday, there will be someone in good and bad luck. All these luck (ie when good and bad etc) can be determined using your Bazi. From your Bazi, we will know when you go thru good times and bad times. But this is more of Destiny analyis, not marriage. But the concept is similar. For wedding, we want to choose a good day so that events for that day will proceed more smoothly and most importantly, if there are anything bad in the Bazi about marriage, it will pacify the intensity and sometimes save the marriage (depending on how bad it is). This is why we need a good date for our marriage.
For ROM, you can use 18th Oct as well.
Hope this helps.