fetch, send: use httpdate for formatting Date: header

> Oct 07 03:25:59 buzzrelay buzzrelay[676]: 2023-10-07T01:25:59.381211Z ERROR buzzrelay::relay: relay::send Response("{\"error\":\"Invalid Date header: not RFC 2616 compliant date: \\\"Sat, 7 Oct 2023 01:25:58 GMT\\\"\"}")

is it the leading 0 in the day position?

Cargo.lock

@@ -283,6 +283,7 @@ dependencies = [
  "futures",
  "http",
  "http_digest_headers",
+ "httpdate",
  "metrics",
  "metrics-exporter-prometheus",
  "metrics-util",

Cargo.toml

@@ -31,3 +31,4 @@ metrics-util = "0.15"
 metrics-exporter-prometheus = "0.12"
 deunicode = "1.3"
 urlencoding = "2"
+httpdate = "1"

src/fetch.rs

@@ -1,3 +1,4 @@
+use std::time::SystemTime;
 use http::StatusCode;
 use serde::de::DeserializeOwned;
 use sigh::{PrivateKey, SigningConfig, alg::RsaSha256};
@@ -21,8 +22,7 @@ where
         .uri(uri)
         .header("host", &host)
         .header("content-type", "application/activity+json")
-        .header("date", chrono::Utc::now().to_rfc2822()
-            .replace("+0000", "GMT"))
+        .header("date", httpdate::fmt_http_date(SystemTime::now()))
         .header("accept", "application/activity+json")
         .header("digest", digest_header)
         .body(vec![])?;

src/send.rs

@@ -1,6 +1,6 @@
 use std::{
     sync::Arc,
-    time::Instant,
+    time::{Instant, SystemTime},
 };
 use http::StatusCode;
 use metrics::histogram;
@@ -39,8 +39,7 @@ pub async fn send_raw(
         .uri(uri)
         .header("host", &host)
         .header("content-type", "application/activity+json")
-        .header("date", chrono::Utc::now().to_rfc2822()
-            .replace("+0000", "GMT"))
+        .header("date", httpdate::fmt_http_date(SystemTime::now()))
         .header("digest", digest_header)
         .body(body.as_ref().clone())
         .map_err(Error::HttpReq)?;