Import a subset of photos based on date I am importing thousands of photos off an SD card. About 15k images, mostly time-lapse. They are from different times so about 4 sets 3-4 images, I want to import each set as a separate album.
Scrolling that many images is a huge pain, can I automatically select or import based on date ranges?

Also, is importing just copying the files - could I use another application to copy based on date range instead? I do not know if the Photos Library is actually a directory structure?
Import the photos to a folder on your Mac. Then you can use smart folders and spotlight and fast file operations to delete / move / Pre-process the files. 

Photos is absolutely not a folder oriented Storage system. Check out Photo Mechanic by camera bits for a folder oriented workflow. 

We use that and high speed SD card readers and can ingest about 100,000 images from 18 cards in a couple hours with 2018 or newer MacBook Pro. Look for USB-C SD card readers. 


Lexar Pro thunderbolt is about $100 each - LRWCR2TBNA
Lexar Pro USB is around $40 each - LRWCR1TBNA


You can even get stacks if you know you’ll have this workflow, but we just use gaffers tape to hold things secure on heavy ingest days around major sporting events.