2 years ago I challenged myself to only eat seasonal and 90% local for one year. I researched ahead of time and made up my own list of foods roughly by the month of seasonality. This meant no cucumbers or tomatoes in January, for example. Winter was mainly certain greens, like kale, as well as storage veggies like onions, carrots, squashes, parsnips, etc.
The result was lower grocery bills, and a much greater appreciation for those first fruits and vegetables of summer. I no longer eat strictly seasonal or local, but the knowledge is now in my subconscious so menu and grocery planning follows the seasons more closely and my grocery bill has not creeped up much since the experiment.
** Full disclosure: I do live in a coastal region with a nearly year around growing season. Eating seasonally without a lot of food preservation would be more difficult in somewhere like North Dakota.
As for events, I plan in the winter for the events of summer, and I keep winter events cheaper to make up for summer expenses. If I know I will need an outfit for a summer wedding next year, for example, I would either begin shopping second hand throughout winter for it or I would shop the year end summer sales the year before. I plan vacations in fall, so I can watch for deals throughout winter (example, a cabin resort in an area we were planning to travel one year had a black Friday sale - book your summer trip at winter prices, one day only). I also purposefully plan for less expensive winter stuff. Save eating out al fresco at a favorite restaurant when we have summer visitors, in winter plan for inexpensive potlucks with friends inside our cozy homes instead.
