What times do section names correspond to?

The short answer

For regular-semester lectures, treat the letter as a time-block code. A–H mostly mean WF; S–Z mean the same clock starts on TTh. Digits and trailing L / R / C mark parallel groups, labs, recitations, and computational labs. Thesis and special-problem sections use faculty-style codes, not the clock ladder.

NSTP, HK, GI, residency, and ROTC / MS use different section grammars — college/component codes, activity titles, or enrollment placeholders. See NSTP, HK, GI, residency, ROTC. Graduate research uses course numbers 200+ / 300+ / 400+ with advisor-style section codes.

The AMIS schedule row remains the source of truth. Codes below are a preview built from Room TBA’s imported rows.

Activity type codes

These are the twelve type values present in Room TBA’s classes table. Row counts are across all imported terms.

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How a section label is built

A section string is usually parent letter(s) + optional group number + optional activity suffix. Read left to right.

Every single-letter code

Letters that appear as standalone section codes in Room TBA. Letters J, K, L, M, N, O, P, Q, R do not appear as single-letter sections in the archive. L and R show up as lab/recit suffixes instead.

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Every two-letter LEC code

All distinct two-letter lecture section codes in the archive, sorted A→Z. High-count pairs are usually adjacent letters from the same day family (AB, CD, ST, UV). Codes such as BD, EF, TV, WX, YZ often mark three-hour single-day meetings that still sit near those letter blocks.

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50 distinct two-letter LEC codes. Counts are LEC rows only; the same string can appear again as a lab parent or with digits (AB1, ST2).

Numbers and L / R / C suffixes

• Digits (AB1, ST3, B2) — parallel lecture sections in the same letter family. About 5,600 one-letter+digit and 1,800 two-letter+digit LEC rows in the archive.
• L — laboratory. Compact (B3L, ST11L) or dashed (G-1L, UV-2L). ~11,900 LAB rows end in L. The parent lecture is the letter run before the number; the lab clock is independent.
• R — recitation (RCT). Compact (AB2R) or dashed (UV-1R). All 203 RCT rows in Room TBA use an R suffix. Planner offerings bundle the parent LEC with its RCT.
• C — computational lab (CPT), e.g. AB-1C, UV-2C.
• Bare nL — labs without a parent letter (CHEM, PHYS, ENSC). Still type LAB; no WF/TTh preview from a letter.

NSTP, HK, GI, residency, and ROTC

These courses show up often in student schedules but do not follow the undergrad lecture letter ladder the same way. Counts are all imported terms in Room TBA (July 16, 2026 census).

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NSTP section prefixes

NSTP 1 and NSTP 2 sections are almost all LEC. The letter run before the digits is a college / unit offering code, not a clock letter. A trailing C or L before the number usually marks CWTS vs LTS (civilian components). RO1* / RO2* mark ROTC platoons.

Examples: ASC3 = AS + CWTS + group 3; ASL7 = AS + LTS + group 7; EN4 = Engineering group 4; RO1A = ROTC. Typical NSTP meeting is a single weekday 3-hour block (often Monday).

HK 11 and HK 12

HK 12 is the PE activity course. Room TBA stores the activity inside course_title (for example “Human Kinetics Activities (Badminton)”). Section codes reuse AB/ST/UV-style pairs with digits, and many rows are typed LAB even when the meeting is the main activity. HK 11 is the wellness lecture; same section shape, usually type LEC.

GI and residency

GI . (Guidance Instructions) is a required advising course with 1-hour slots. Section codes look like academic letters but do not track the WF/TTh ladder reliably.

RESIDENCY (UGRD) and RESIDENCY (GRD) are type IND with sections UGRD / GRAD and empty schedules. They keep a student enrolled without a meeting time. Do not confuse them with RES 201– RES 205 (Resilience Studies), which are ordinary academic lectures.

No separate PATHFIT / PE / CWTS / LTS course codes appear in Room TBA beyond NSTP and HK; those components live inside NSTP section prefixes or HK activity titles.

MS / PhD course numbers (200+, 300+, 400+)

UPLB course numbers encode level. In campus talk, people often say 200+ for master’s work and 300+ for doctoral work. Room TBA’s imported rows are a bit finer-grained — read the title and type, not only the number.

Practical decoding:

• 200 titled “Undergraduate Thesis” / “Major Practice” → senior undergrad research (type THE / PRA), not an MS class.
• 200–299 LEC with a real subject title (e.g. AENG 201 Advanced Engineering Mathematics) → graduate coursework; may still show a letter section.
• 300 titled “Master's Thesis” → MS research (type THE).
• 400+ titled “Dissertation” / “Doctoral Dissertation” → PhD research (type THE or DSR).

Section codes on research courses

Census from prod classes (all terms). Do not use A–H / S–Z time inference on THE / SPR / DSR / IND rows.

What changed across terms

Oldest archive term is CRS 1231 (AY 2023–2024 1st semester); newest is 1261 (AY 2026–2027 1st). Reading AMIS exports through the same normalizer, the calendar barely moved. What jumped in Room TBA’s table is mostly import scope.

Schedule shape (stable)

• Regular-semester scheduled LEC slots stay on the same mix: ~35–38% TTh, ~31–33% WF, ~26–31% single-day. That band holds from 1231 through 1261.
• 90-minute blocks remain the modal length (~1,300–1,500 LEC slots per regular term). Three-hour (180 min) single-day lectures stay a minority (~300–390 slots).
• Peak starts stay 1:00 PM, 10:00 AM, 4:00 PM, then 8:30 / 9:00 AM. the letter-ladder clocks.
• Midyear (1243, 1253) is a different calendar every year: ~71–73% dense MTWThFS, almost no WF, and 105-minute blocks (not 90). That is semester type, not a multi-year drift.

Room TBA row counts (import policy)

• Terms 1231–1243 and midyear 1253 in prod are still mostly LEC + LAB (~4.8k–5.1k regular; ~230 midyear). AMIS itself already had ~4k THE rows each term; Room TBA simply did not import them yet.
• 1251 adds RCT (~100) and a small THE/SPR/PRA/DSR trickle (~300). Scheduled LEC count is unchanged in shape.
• 1252 and 1261 jump to ~12.6k–12.9k DB rows because the importer started keeping thesis / SP / practicum / dissertation with null rooms (~7.5k roomless rows). AMIS LEC/LAB volume did not double. Room TBA’s catalog got wider.

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Likely reasons

• Import policy, not campus growth. AMIS regular-term dumps stay ~11k–13k rows across the archive. The DB doubling at 1252/1261 matches turning on NON_ROOM types (THE/SPR/PRA/DSR/IND) in the importer, plus RCT for the planner. see room-scheduled-types.ts.
• Letter ladder still maps the same grid. Stable TTh/WF shares mean A–H / S–Z time inference did not rot between AY 2023–2024 and AY 2026–2027.
• Midyear is a fixed alternate calendar. Dense daily meetings and 105-minute offsets appear in both 1243 and 1253; do not read them as a trend away from WF/TTh.
• 1261 scheduled LEC is a bit lower (2,466 vs ~2,600–2,800 earlier). Early-term / incomplete offering data is the boring explanation; re-check after COM if the gap remains.

Day % are shares of normalized LEC schedule slots from local AMIS JSON caches (not raw mon–sat flags). DB row counts are prod classes as of July 16, 2026.

Regular semester day structure

Among 2,653 lecture slots in term 1252 (AY 2025–2026 2nd semester), about 70% sit on the TTh/WF ladder that the letter code assumes. The rest are mostly single-day blocks.

About 55% of those LEC slots are 90 minutes long (1,472 of 2,653). On the TTh+WF pairs alone, 90-minute meetings make up about 78% of the slots. Peaks land on the wiki starts: 8:30, 10:00, 1:00, 2:30, 4:00, and the early/late edges at 7:00 and 5:30. Single-day lectures are often three hours (for example 1:00–4:00 PM or 9:00–12:00) on one weekday.

Midyear is a different calendar

Term 1253 (AY 2025–2026 midyear) had 132 scheduled lecture slots in Room TBA. About 69% meet MTWThFS (six days a week). About 86% are 105-minute blocks that start on :45 or :15 offsets, not the regular :00/:30 ladder.

Four windows hold most midyear lectures (~61% of LEC slots):

• 8:45–10:30
• 10:30–12:15
• 1:00–2:45
• 2:45–4:30

Weekly contact for a typical midyear LEC is about 10.5 hours (6 × 105 min), versus roughly 3 hours for a regular TTh or WF paired lecture (2 × 90 min). Same course credit, denser calendar. Do not use A–H / S–Z inference for midyear or for *L labs.

Midyear labs lean on MWF, TThS, or TWThF rather than daily MTWThFS. Lengths cluster around 210 minutes, with occasional multi-hour marathons.

Midyear section names

Midyear reuses the same alphabet soup as regular semesters, then bends it. Single letters A–H still dominate lecture labels (C, B, H, G are the busiest in the CRS 1253 AMIS export), but those rows meet MTWThFS — so the regular “A–H = WF” rule is false for midyear. S–Z singles are rare.

Departments also invent cross-ladder compounds: one section string that concatenates a WF-family pair with a TTh-family pair so the name covers a long daily block.

Cross-ladder compounds (CRS 1253)

Observed on midyear AMIS lecture rows (e.g. CHEM 32 BCTU / FGXY on MTWThFS). Treat these as midyear labels, not as “take both a BC and a TU regular-sem section.”

When the letter is useful

How we checked

Glossary tables enumerate every type value and every single-letter and two-letter LEC section observed in the prod classes table as of July 16, 2026.

The letter-ladder match scan covered 35,607 class records across nine terms (AY 2023–2024 through AY 2026–2027). Pattern match used 8,917 scheduled single-letter lectures from seven regular semesters: 7,804 matched (87.5%).

Day-structure figures use CRS terms 1252 and 1253 LEC slots only (July 16, 2026 pass). The across-terms table normalizes every local data/amis-*.json cache from CRS 1231 through 1261 and compares against prod row counts.