I completely understand where you're coming from. I also want my email communications to be efficient and professional, especially when dealing with specific dates and times. For my needs, I found that using an email marketing platform like Mailchimp or ActiveCampaign could be really beneficial. They allow for automation and can handle custom data imports from spreadsheets quite well.

With Mailchimp, for example, you can import your list directly without needing to select each date and time manually from dropdowns. Instead, you can set up an automation to trigger the emails exactly 24 hours before the specified events in your spreadsheet. ActiveCampaign offers similar functionality with a focus on automation and better customization for email design, which might help in achieving that professional look you're aiming for.

I recommend checking if these platforms allow you to format your email templates according to your branding needs, as this could definitely elevate the professionalism of your communications. It might take some initial setup, but in the long run, it'll save us both a lot of time and effort!