The conversion date is effectively the system start date, the date from which you will start entering your day-to-day transactions into the new system. It is your "opening balance date" for the new system.
By default the conversion date is set to the first day of the month in which you initially set up your trial. You can, of course, change this later in the Settings area via Settings > Agency > Financial > Start (Conversion) Date.
Rent and charges
Once you have defined your start date, the system will only automatically apply rent and charges from that start date onwards. If you have a tenancy which started on 1 January 2018 at 1000.00 per month, but you have set your start date to 1 October 2018, then the system will only automatically apply rent from 1 October onwards. It assumes that all activity before this date is the concern of the old system.
However, you may have rent arrears and outstanding charges, so you can of course manually add one-off rent and charges for dates prior to the start date to reflect these unpaid or outstanding balances.
Receipts and payouts
It is not possible to record receipts into bank accounts, or payouts from bank accounts, for dates prior to your conversion or system start date.
If suppliers or landlords have been paid prior to this date then those will be recorded in your old system, so they are not within the scope of the new system.
If tenants (or landlords) have made overpayments prior to the start date then these may be added as credits on the relevant account where they may then be allocated to outstanding balances, or refunded if appropriate.
Changing the start date
Any user with accounting privileges can change the conversion date, but be very careful when doing so as it redraws the line in the sand for when you started to use the new system and will adjust all of your opening balances accordingly.