rm dependence on chrono, replace with time 0.3.11 (chronotope/chrono#499)

Author: cdstanford

Cargo.lock

@@ -7,12 +7,12 @@ edition = "2018"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-chrono = "0.4.15"
 disjoint-sets = "0.4.2"
 rand = "0.8.5"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 structopt = "0.3.21"
+time = { version = "0.3.11", features = ["formatting"] }
 
 [lib]
 doctest = false

Cargo.toml

@@ -4,14 +4,14 @@
     (File I/O, JSON serialization, system time, etc.)
 */
 
-use chrono::offset::Local;
 use serde::de::DeserializeOwned;
 use serde::ser::Serialize;
 use std::fmt::Debug;
 use std::fs::{self, File};
 use std::io::{self, BufReader, BufWriter, Write};
 use std::path::{Path, PathBuf};
 use std::time::{Duration, SystemTime};
+use time::{format_description, OffsetDateTime};
 
 /*
     File I/O
@@ -134,8 +134,16 @@ pub fn time_since(t: &SystemTime) -> Duration {
 }
 
 // Current datetime for use in file names
+// Note: removed dependence on chrono on 2022-07-19; as a result,
+// now this uses time::OffsetDateTime, which is UTC rather than local time.
 pub fn current_datetime_str() -> String {
-    Local::now().format("%Y-%m-%d-%H%M%S").to_string()
+    let dt: OffsetDateTime = SystemTime::now().into();
+    let dt_fmt = format_description::parse(
+        "[year]-[month]-[day]-[hour][minute][second]"
+    ).unwrap();
+    dt.format(&dt_fmt).unwrap()
+    // Old implementation using Chrono
+    // Local::now().format("%Y-%m-%d-%H%M%S").to_string()
 }
 
 #[test]