The recommended time to apply is at least 3 weeks before travelling to Spain on business. While the earliest that you can apply is 6 months, the latest that you can apply is at least 15 days before your trip to Spain on business.
Because some forms of travel purposes can take longer than normal to process, we suggest that you apply at least 20 working days before the date you wish to depart. For example, from the time of your appointment, your Schengen Visa application will be processed in 5-15 working days.