OK, it’s been three weeks already, but I hadn’t seen it. Monsur explains that
"Bloglet’s RSS support only fully extends to RSS feeds that support item-level dates. This means your RSS feed needs the pubDate or dc:date tag (if it doesn’t, all the posts in your RSS feed will be sent, which may or may not be what you want). I want to find a way around this. However to sort out a blog’s daily posts when the posts don’t have a publication date can be a formidable task, and one that doesn’t fit into Bloglet’s current programming model."